[libc-commits] [libc] Remove wrong float-128 extension for CLang (PR #75909)

[Guillaume Chatelet via libc-commits]

gchatelet wrote:

The issue seems to be coming from OS support
https://godbolt.org/z/Y94o7KEKx

It is supported for `--target=x86_64-pc-linux-eabi` but not for `--target=x86_64-pc-none-eabi` nor `--target=x86_64-pc-win32-eabi`. So the proper guard should be:
```
#if (defined(LIBC_COMPILER_CLANG_VER) && (LIBC_COMPILER_CLANG_VER >= 600)) &&  \
    (defined(LIBC_TARGET_ARCH_IS_X86_64) &&                                    \
     defined(LIBC_TARGET_OS_IS_LINUX) && !defined(LIBC_TARGET_OS_IS_FUCHSIA))
#define LIBC_COMPILER_HAS_FLOAT128_EXTENSION
#endif
```

https://github.com/llvm/llvm-project/pull/75909