Fixed MINGW compile errors

qgroundcontrol.pri

@@ -366,15 +366,13 @@ win32-g++ {
     RC_FILE = $$BASEDIR/qgroundcontrol.rc
 
     # Copy dependencies
-    BASEDIR_WIN = $$replace(BASEDIR,"/","\\")
-    TARGETDIR_WIN = $$replace(TARGETDIR,"/","\\")
 
-    QMAKE_PRE_LINK += && copy /Y \"$$BASEDIR_WIN\lib\sdl\win32\SDL.dll\" \"$$TARGETDIR_WIN\debug\SDL.dll\"
-    QMAKE_PRE_LINK += && copy /Y \"$$BASEDIR_WIN\lib\sdl\win32\SDL.dll\" \"$$TARGETDIR_WIN\release\SDL.dll\"
-    QMAKE_PRE_LINK += && xcopy \"$$BASEDIR_WIN\audio\" \"$$TARGETDIR_WIN\debug\audio\" /S /E /Y
-    QMAKE_PRE_LINK += && xcopy \"$$BASEDIR_WIN\audio\" \"$$TARGETDIR_WIN\release\audio\" /S /E /Y
-    QMAKE_PRE_LINK += && xcopy \"$$BASEDIR_WIN\models\" \"$$TARGETDIR_WIN\debug\models\" /S /E /Y
-    QMAKE_PRE_LINK += && xcopy \"$$BASEDIR_WIN\models\" \"$$TARGETDIR_WIN\release\models\" /S /E /Y
+    QMAKE_PRE_LINK += && cp $$BASEDIR_WIN/lib/sdl/win32/SDL.dll $$TARGETDIR_WIN/debug/SDL.dll
+    QMAKE_PRE_LINK += && cp $$BASEDIR_WIN/lib/sdl/win32/SDL.dll $$TARGETDIR_WIN/release/SDL.dll
+    QMAKE_PRE_LINK += && cp -r $$BASEDIR_WIN/audio $$TARGETDIR_WIN/debug/audio
+    QMAKE_PRE_LINK += && cp -r $$BASEDIR_WIN/audio $$TARGETDIR_WIN/release/audio
+    QMAKE_PRE_LINK += && cp -r $$BASEDIR_WIN/models $$TARGETDIR_WIN/debug/models
+    QMAKE_PRE_LINK += && cp -r $$BASEDIR_WIN/models $$TARGETDIR_WIN/release/models
 
     # osg/osgEarth dynamic casts might fail without this compiler option.
     # see http://osgearth.org/wiki/FAQ for details.