Fix __float128 only available on Linux for x86_64 (#75909)

Author: silver-popov

libc/src/__support/macros/properties/float.h

@@ -59,9 +59,9 @@ using float16 = _Float16;
      defined(LIBC_TARGET_ARCH_IS_X86_64))
 #define LIBC_COMPILER_HAS_C23_FLOAT128
 #endif
-#if (defined(LIBC_COMPILER_CLANG_VER) && (LIBC_COMPILER_CLANG_VER >= 500)) &&  \
+#if (defined(LIBC_COMPILER_CLANG_VER) && (LIBC_COMPILER_CLANG_VER >= 600)) &&  \
     (defined(LIBC_TARGET_ARCH_IS_X86_64) &&                                    \
-     !defined(LIBC_TARGET_OS_IS_FUCHSIA))
+     defined(LIBC_TARGET_OS_IS_LINUX) && !defined(LIBC_TARGET_OS_IS_FUCHSIA))
 #define LIBC_COMPILER_HAS_FLOAT128_EXTENSION
 #endif