[CMAKE] Elimitate the use of GCC and CLANG variables

sdk/lib/3rdparty/freetype/CMakeLists.txt

@@ -58,6 +58,8 @@ add_library(freetype ${SOURCE})
 if(CMAKE_C_COMPILER_ID STREQUAL "MSVC" AND ARCH STREQUAL "amd64")
     # error C4312: 'type cast': conversion from 'unsigned long' to 'void *' of greater size
     remove_target_compile_option(freetype "/we4312")
-elseif(GCC)
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(freetype PRIVATE -fno-builtin-malloc)
 endif()

sdk/lib/3rdparty/libxml2/CMakeLists.txt

@@ -64,7 +64,7 @@ list(APPEND SOURCE
 
 add_library(libxml2 ${SOURCE})
 
-if(MSVC AND (NOT USE_CLANG_CL))
+if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
     # Unreferenced local variable
     remove_target_compile_option(libxml2 "/we4101")
     target_compile_options(libxml2 PRIVATE "/wd4101")

sdk/lib/crt/msvcrtex.cmake

@@ -26,7 +26,7 @@ if(ARCH STREQUAL "i386")
         math/i386/alldiv_asm.s
         math/i386/aulldiv_asm.s
         )
-    if (GCC AND CLANG)
+    if (CMAKE_C_COMPILER_ID STREQUAL "Clang" AND NOT MSVC)
         list(APPEND MSVCRTEX_ASM_SOURCE
             math/i386/ceilf.S
             math/i386/floorf.S)
@@ -77,7 +77,7 @@ if(MSVC AND (ARCH STREQUAL "i386"))
 endif()
 
 
-if(GCC OR CLANG)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(msvcrtex PRIVATE $<$<COMPILE_LANGUAGE:C>:-Wno-main>)
     if(LTCG)
         target_compile_options(msvcrtex PRIVATE -fno-lto)

sdk/lib/drivers/wdf/CMakeLists.txt

@@ -210,7 +210,7 @@ target_include_directories(wdf01000
 
 target_link_libraries(wdf01000 aux_klib ntoskrnl_vista ${PSEH_LIB})
 
-if(GCC)
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     target_compile_options(wdf01000
         PRIVATE -Wno-write-strings -Wno-unknown-pragmas -Wno-switch
         PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-Wno-reorder -Wno-invalid-offsetof -Wno-delete-non-virtual-dtor>)

sdk/lib/rtl/CMakeLists.txt

@@ -5,7 +5,7 @@ add_definitions(
     -D_NTSYSTEM_
     -D_NTDLLBUILD_)
 
-if (GCC)
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU" OR CMAKE_C_COMPILER_ID STREQUAL "Clang")
     # Enable this again. CORE-17637
     add_compile_options(-Wunused-result)
 endif()