[compiler-rt] [compiler-rt][builtins] Fix FLOAT16 feature detection (PR #69842)

[via llvm-commits]

gulfemsavrun wrote:

We started seeing `SanitizerCommon-tsan` test failures after this patch.
```
FAIL: SanitizerCommon-tsan-x86_64-Linux :: Linux/abort_on_error.cpp (3645 of 15728)
******************** TEST 'SanitizerCommon-tsan-x86_64-Linux :: Linux/abort_on_error.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 4: /b/s/w/ir/x/w/llvm_build/./bin/clang  --driver-mode=g++ -gline-tables-only -fsanitize=thread  -funwind-tables --sysroot=/b/s/w/ir/x/w/cipd/linux  -I/b/s/w/ir/x/w/llvm-llvm-project/compiler-rt/test -ldl /b/s/w/ir/x/w/llvm-llvm-project/compiler-rt/test/sanitizer_common/TestCases/Linux/abort_on_error.cpp -o /b/s/w/ir/x/w/llvm_build/runtimes/runtimes-x86_64-unknown-linux-gnu-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Linux/Output/abort_on_error.cpp.tmp
+ /b/s/w/ir/x/w/llvm_build/./bin/clang --driver-mode=g++ -gline-tables-only -fsanitize=thread -funwind-tables --sysroot=/b/s/w/ir/x/w/cipd/linux -I/b/s/w/ir/x/w/llvm-llvm-project/compiler-rt/test -ldl /b/s/w/ir/x/w/llvm-llvm-project/compiler-rt/test/sanitizer_common/TestCases/Linux/abort_on_error.cpp -o /b/s/w/ir/x/w/llvm_build/runtimes/runtimes-x86_64-unknown-linux-gnu-bins/compiler-rt/test/sanitizer_common/tsan-x86_64-Linux/Linux/Output/abort_on_error.cpp.tmp
ld.lld: error: undefined symbol: __gcc_personality_v0
>>> referenced by abort_on_error.cpp
>>>               /b/s/w/ir/x/t/lit-tmp-ltnvtf5j/abort_on_error-0ca4b8.o:(DW.ref.__gcc_personality_v0)
clang: error: linker command failed with exit code 1 (use -v to see invocation)

--

********************
```
https://logs.chromium.org/logs/fuchsia/led/gulfem_google.com/141f7eb5f57d1686c0532c0155e6deca355b20629e48dedea6078c47d6e7a825/+/u/clang/test/stdout

https://github.com/llvm/llvm-project/pull/69842