[clang] [clang-tools-extra] [llvm] [clang][headers] Need a way for math.h to share the definitions of INIFINITY and NAN with float.h (PR #164348)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-flang-rhel-clang` running on `ppc64le-flang-rhel-test` while building `clang-tools-extra,clang,llvm` at step 6 "test-build-unified-tree-check-flang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/157/builds/41740

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

```
Step 6 (test-build-unified-tree-check-flang) failure: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
9.145 [4/29/0] cd /home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/runtimes/runtimes-bins && /home/buildbots/llvm-external-buildbots/cmake-3.31.2/bin/cmake --build /home/buildbots/llvm-external-buildbots/workers/ppc64le-flang-rhel-test/ppc64le-flang-rhel-clang-build/build/runtimes/runtimes-bins/ --target libomp-mod --config Release
ninja: no work to do.
9.320 [2/4/28] Building CXX object tools/flang/unittests/Frontend/CMakeFiles/FlangFrontendTests.dir/CodeGenActionTest.cpp.o
9.753 [1/3/30] Linking CXX executable tools/flang/unittests/Common/FlangCommonTests
14.104 [1/2/31] Linking CXX executable tools/flang/unittests/Optimizer/FlangOptimizerTests
23.935 [1/1/32] Linking CXX executable tools/flang/unittests/Frontend/FlangFrontendTests
23.936 [0/1/32] Running the Flang regression tests
command timed out: 1200 seconds without output running [b'ninja', b'check-flang'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=1224.558701

```

</details>

https://github.com/llvm/llvm-project/pull/164348