[libc] Replace LLVM_COMPILER_IS_GCC_COMPATIBLE with a local check. (#119164)

Author: lntue

libc/cmake/modules/LLVMLibCCompileOptionRules.cmake

@@ -1,3 +1,15 @@
+if(NOT DEFINED LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
+  if(CMAKE_COMPILER_IS_GNUCXX)
+    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
+  elseif( MSVC )
+    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE OFF)
+  elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang" )
+    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
+  elseif( "${CMAKE_CXX_COMPILER_ID}" MATCHES "Intel" )
+    set(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE ON)
+  endif()
+endif()
+
 function(_get_compile_options_from_flags output_var)
   set(compile_options "")
 
@@ -8,7 +20,7 @@ function(_get_compile_options_from_flags output_var)
   check_flag(ADD_EXPLICIT_SIMD_OPT_FLAG ${EXPLICIT_SIMD_OPT_FLAG} ${ARGN})
   check_flag(ADD_MISC_MATH_BASIC_OPS_OPT_FLAG ${MISC_MATH_BASIC_OPS_OPT_FLAG} ${ARGN})
 
-  if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+  if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
     if(ADD_FMA_FLAG)
       if(LIBC_TARGET_ARCHITECTURE_IS_X86_64)
         list(APPEND compile_options "-mavx2")
@@ -96,7 +108,7 @@ function(_get_common_compile_options output_var flags)
 
   set(compile_options ${LIBC_COMPILE_OPTIONS_DEFAULT} ${compile_flags} ${config_flags})
 
-  if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+  if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
 
     if(LLVM_LIBC_FULL_BUILD)
@@ -210,7 +222,7 @@ function(_get_common_test_compile_options output_var c_test flags)
       ${LIBC_TEST_COMPILE_OPTIONS_DEFAULT}
       ${compile_flags})
 
-  if(LLVM_COMPILER_IS_GCC_COMPATIBLE)
+  if(LLVM_LIBC_COMPILER_IS_GCC_COMPATIBLE)
     list(APPEND compile_options "-fpie")
 
     if(LLVM_LIBC_FULL_BUILD)