Run sanitizer single flag checks for all platforms

When checking for the availability of a sanitizer set, it would only run
`check_cxx_source_compiles` for the full set of flags, and additionally
`check_cxx_compiler_flag` on WIN32.

Now, it performs both checks for all platforms.

Author: StableCoder

sanitizers.cmake

@@ -117,12 +117,10 @@ function(test_san_flags RETURN_VAR LINK_OPTIONS)
   unset(CMAKE_REQUIRED_FLAGS)
   unset(test_san_flags_OPTION_TEST CACHE)
   foreach(ARG ${ARGN})
-    if(WIN32)
-      unset(test_san_flags_OPTION_TEST CACHE)
-      check_cxx_compiler_flag(${ARG} test_san_flags_OPTION_TEST)
-      if(NOT test_san_flags_OPTION_TEST)
-        break()
-      endif()
+    unset(test_san_flags_OPTION_TEST CACHE)
+    check_cxx_compiler_flag(${ARG} test_san_flags_OPTION_TEST)
+    if(NOT test_san_flags_OPTION_TEST)
+      break()
     endif()
     set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} ${ARG}")
   endforeach()