Make it explicit which configuration settings are meant for MinGW.

Source/CMake/Modules/Urho3D-CMake-common.cmake

@@ -21,10 +21,10 @@
 #
 
 # Certain MinGW versions fail to compile SSE code. This is the initial guess for known "bad" version range, and can be tightened later
-if (WIN32 AND NOT MSVC)
+if (MINGW)
     execute_process(COMMAND ${CMAKE_C_COMPILER} -dumpversion OUTPUT_VARIABLE GCC_VERSION)
     if (GCC_VERSION VERSION_LESS 4.9.1)
-        message ("Disabling SSE by default due to MinGW version. It is recommended to upgrade to MinGW with GCC >= 4.9.1. You can also try to re-enable SSE with CMake option -DURHO3D_SSE=1, but this may result in compile errors.")
+        message (WARNING "Disabling SSE by default due to MinGW version. It is recommended to upgrade to MinGW with GCC >= 4.9.1. You can also try to re-enable SSE with CMake option -DURHO3D_SSE=1, but this may result in compile errors.")
         set (URHO3D_DEFAULT_SSE FALSE)
     else ()
         set (URHO3D_DEFAULT_SSE TRUE)
@@ -286,7 +286,7 @@ else ()
             endif ()
         endif ()
         # MinGW-specific setup
-        if (WIN32)
+        if (MINGW)
             set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -static -static-libgcc -fno-keep-inline-dllexport")
             set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static -static-libstdc++ -static-libgcc -fno-keep-inline-dllexport")
             set (CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -static")