[clang] Search for @_thisIsNotAPipe vs _thisIsNotAPipe (PR #192132)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-aarch64-darwin` running on `doug-worker-5` while building `clang` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/190/builds/41661

<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 :: CodeGen/2008-07-31-asm-labels.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 1
/Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/lib/clang/23/include -nostdsysteminc -emit-llvm -o /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/CodeGen/2008-07-31-asm-labels.c
# executed command: /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/clang -cc1 -internal-isystem /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/lib/clang/23/include -nostdsysteminc -emit-llvm -o /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/CodeGen/2008-07-31-asm-labels.c
# .---command stderr------------
# | /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/CodeGen/2008-07-31-asm-labels.c:11:6: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C23, conflicting with a subsequent declaration [-Wdeprecated-non-prototype]
# |    11 | void pipe() asm("_thisIsNotAPipe");
# |       |      ^
# | /Users/buildbot/buildbot-root2/aarch64-darwin/llvm-project/clang/test/CodeGen/2008-07-31-asm-labels.c:17:6: note: conflicting prototype is here
# |    17 | void pipe(int);
# |       |      ^
# | 1 warning generated.
# `-----------------------------
# RUN: at line 2
not grep "@pipe()" /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp
# executed command: not grep '@pipe()' /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp
# note: command had no output on stdout or stderr
# RUN: at line 3
grep '@_thisIsNotAPipe' /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp | /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/count 3
# executed command: grep @_thisIsNotAPipe /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/tools/clang/test/CodeGen/Output/2008-07-31-asm-labels.c.tmp
# note: command had no output on stdout or stderr
# error: command failed with exit status: 1
# executed command: /Volumes/ExternalSSD/buildbot-root/aarch64-darwin/build/bin/count 3
# .---command stderr------------
# | Expected 3 lines, got 0.
# `-----------------------------
# error: command failed with exit status: 1

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/192132