Record compile features for GNU on Windows (#15443)

Drop the 'UNIX' condition on GNU compiler features.

Suggested-by: David Demelier <[email protected]>

Modules/Compiler/GNU-CXX.cmake

@@ -44,10 +44,10 @@ macro(cmake_record_cxx_compile_features)
   endmacro()
 
   set(_result 0)
-  if (UNIX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.8)
     _get_gcc_features(${CMAKE_CXX14_STANDARD_COMPILE_OPTION} CMAKE_CXX14_COMPILE_FEATURES)
   endif()
-  if (UNIX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
+  if (NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
     if (_result EQUAL 0)
       _get_gcc_features(${CMAKE_CXX11_STANDARD_COMPILE_OPTION} CMAKE_CXX11_COMPILE_FEATURES)
     endif()