[clang] [analyzer] Fix false positive in strchr/strrchr with constant args (PR #210154)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-ubuntu-fast` running on `sie-linux-worker` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/60200

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'Clang :: Analysis/string-search-modeling.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang -cc1 -internal-isystem /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/../lib/clang/include -nostdsysteminc -analyze -setup-static-analyzer -verify /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c    -analyzer-checker=core,unix    -analyzer-checker=debug.ExprInspection    -analyzer-config eagerly-assume=false
# executed command: /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/clang -cc1 -internal-isystem /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/../lib/clang/include -nostdsysteminc -analyze -setup-static-analyzer -verify /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c -analyzer-checker=core,unix -analyzer-checker=debug.ExprInspection -analyzer-config eagerly-assume=false
# .---command stderr------------
# | error: 'expected-error' diagnostics seen but not expected: 
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 515: use of undeclared identifier 'u'
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 527: use of undeclared identifier 'u'
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 538: use of undeclared identifier 'U'
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 550: use of undeclared identifier 'u'
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 578: use of undeclared identifier 'u'
# | error: 'expected-warning' diagnostics expected but not seen: 
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 25 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:26): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 31 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:32): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 37 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:38): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 43 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:44): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 49 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:50): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 55 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:56): Address of stack memory associated with local variable 'buf' returned to caller
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 73 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:74): Null pointer passed as 1st argument to strchr()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 78 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:79): Null pointer passed as 1st argument to strrchr()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 83 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:84): Null pointer passed as 1st argument to memchr()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 88 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:89): Null pointer passed as 1st argument to strstr()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 93 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:94): Null pointer passed as 1st argument to strpbrk()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 98 (directive at /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c:99): Null pointer passed as 1st argument to strchrnul()
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 108: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 108: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 109: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 109: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 110: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 110: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 111: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 111: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 112: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 112: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 117: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 125: UNKNOWN
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 126: UNKNOWN
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 132: Argument to 'free()' is the address of a global variable, which is not memory allocated by 'malloc()'
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 145: Attempt to release already released memory
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 157: Dereference of null pointer
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 176: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 177: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 193: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 197: FALSE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 202: TRUE
# |   File /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/clang/test/Analysis/string-search-modeling.c Line 206: TRUE
...

```

</details>

https://github.com/llvm/llvm-project/pull/210154