[CMAKE] Some options are only supported by GCC, don't use them for clang

These are (so far):
-Wno-format-overflow
-Wno-nonnull-compare
-Wno-old-style-declaration
-Wno-unused-but-set-variable

drivers/filesystems/ext2/CMakeLists.txt

@@ -103,9 +103,10 @@ else()
     target_compile_options(ext2fs PRIVATE
         -Wno-pointer-sign -Wno-unused-function
         -Wno-unused-variable -Wno-missing-braces)
-    if (NOT CLANG)
-        target_compile_options(ext2fs PRIVATE -Wno-unused-but-set-variable)
-    endif()
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(ext2fs PRIVATE -Wno-unused-but-set-variable)
 endif()
 
 if(CLANG)

drivers/filesystems/ffs/CMakeLists.txt

@@ -35,11 +35,13 @@ if(USE_CLANG_CL OR (NOT MSVC))
     target_compile_options(ffs PRIVATE -Wno-unused-variable -Wno-missing-braces)
     if(USE_CLANG_CL)
         target_compile_options(ffs PRIVATE -Wno-empty-body)
-    else()
-        target_compile_options(ffs PRIVATE -Wno-unused-but-set-variable)
     endif()
 endif()
 
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(ffs PRIVATE -Wno-unused-but-set-variable)
+endif()
+
 add_definitions(-D__KERNEL__)
 set_module_type(ffs kernelmodedriver)
 target_link_libraries(ffs memcmp ${PSEH_LIB})

drivers/filesystems/reiserfs/CMakeLists.txt

@@ -82,7 +82,6 @@ if(USE_CLANG_CL OR (NOT MSVC))
     target_compile_options(reiserfs PRIVATE -Wno-missing-braces -Wno-pointer-sign)
     target_compile_options(reiserfs PRIVATE -Wno-unused-function -Wno-unused-variable)
     if(NOT USE_CLANG_CL)
-        target_compile_options(reiserfs PRIVATE -Wno-unused-but-set-variable)
         target_compile_definitions(reiserfs PRIVATE __GCC__)
     endif()
 else()
@@ -92,6 +91,10 @@ else()
     target_compile_options(reiserfs PRIVATE /wd4189 /wd4142 /wd4101)
 endif()
 
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(reiserfs PRIVATE -Wno-unused-but-set-variable)
+endif()
+
 target_link_libraries(reiserfs memcmp ${PSEH_LIB})
 add_definitions(-D__KERNEL__ -D_CRT_NO_POSIX_ERROR_CODES)
 set_module_type(reiserfs kernelmodedriver)

drivers/filesystems/udfs/CMakeLists.txt

@@ -50,8 +50,10 @@ if(MSVC)
         target_compile_options(udfs PRIVATE -Wno-tautological-unsigned-zero-compare -Wno-self-assign)
         target_compile_options(udfs PRIVATE -Wno-sometimes-uninitialized -Wno-parentheses-equality)
     endif()
-else()
-    target_compile_options(udfs PRIVATE "-Wno-unused-but-set-variable")
+endif()
+
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    target_compile_options(udfs PRIVATE -Wno-unused-but-set-variable)
 endif()
 
 set_module_type(udfs kernelmodedriver)