Always look for winmm under Windows

It's needed for timeGetTime, even if the WinMM backend is disabled

CMakeLists.txt

@@ -280,6 +280,14 @@ IF(NOT HAVE_STDINT_H)
     ENDIF()
 ENDIF()
 
+IF(WIN32)
+    # Windows needs winmm for timeGetTime, even if the backend is disabled
+    CHECK_SHARED_LIBRARY_EXISTS(winmm timeGetTime 0 "" HAVE_LIBWINMM)
+    IF(HAVE_LIBWINMM)
+        SET(EXTRA_LIBS winmm ${EXTRA_LIBS})
+    ENDIF()
+ENDIF()
+
 
 SET(OPENAL_OBJS  OpenAL32/alAuxEffectSlot.c
                  OpenAL32/alBuffer.c