[llvm] [CMake] Re-add -fno-rtti to llvm-config --cxxflags (PR #174084)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-ppc64le-linux-multistage` running on `ppc64le-clang-multistage-test` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/76/builds/13697

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

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'LeakSanitizer-AddressSanitizer-powerpc64le :: TestCases/create_thread_leak.cpp' FAILED ********************
Exit Code: 2

Command Output (stdout):
--
# RUN: at line 3
/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/./bin/clang  --driver-mode=g++ -O0  -m64 -fno-function-sections  -gline-tables-only -fsanitize=address -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/../ -pthread /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp -o /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp
# executed command: /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/./bin/clang --driver-mode=g++ -O0 -m64 -fno-function-sections -gline-tables-only -fsanitize=address -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/../ -pthread /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp -o /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp
# RUN: at line 4
not  /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 1 0 0 2>&1 | FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK123
# executed command: not /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 1 0 0
# executed command: FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK123
# RUN: at line 5
not  /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 0 1 0 2>&1 | FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK234
# executed command: not /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 0 1 0
# executed command: FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK234
# RUN: at line 6
not  /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 0 0 1 2>&1 | FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK234
# executed command: not /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/stage1/runtimes/runtimes-bins/compiler-rt/test/lsan/POWERPC64LEAsanConfig/TestCases/Output/create_thread_leak.cpp.tmp 10 0 0 1
# note: command had no output on stdout or stderr
# error: command failed with exit status: 1
# executed command: FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK234
# .---command stderr------------
# | FileCheck error: '<stdin>' is empty.
# | FileCheck command line:  FileCheck /home/buildbots/llvm-external-buildbots/workers/ppc64le-clang-multistage-test/clang-ppc64le-multistage/llvm/compiler-rt/test/lsan/TestCases/create_thread_leak.cpp --check-prefixes=LEAK,LEAK234
# `-----------------------------
# error: command failed with exit status: 2

--

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


```

</details>

https://github.com/llvm/llvm-project/pull/174084