Features: Reorder the GNU C dialect feature tests

This doesn't make a difference, but the consistency with other files
is easier to reason about.

Modules/Compiler/GNU-C.cmake

@@ -21,12 +21,12 @@ macro(cmake_record_c_compile_features)
   endmacro()
 
   if (UNIX AND NOT APPLE AND NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 4.7)
-    _get_gcc_features(c90 CMAKE_C90_COMPILE_FEATURES)
+    _get_gcc_features(c11 CMAKE_C11_COMPILE_FEATURES)
     if (_result EQUAL 0)
       _get_gcc_features(c99 CMAKE_C99_COMPILE_FEATURES)
     endif()
     if (_result EQUAL 0)
-      _get_gcc_features(c11 CMAKE_C11_COMPILE_FEATURES)
+      _get_gcc_features(c90 CMAKE_C90_COMPILE_FEATURES)
     endif()
   else()
     set(_result 0)