Merge pull request #6912 from John-He-928/mingw-build

fix mingw32/mingw64 compiling
Update lua-template and lua-empty-test for replacing bgMusicPath
Merge branch 'v3' of https://github.com/cocos2d/cocos2d-x into v3_fix
Merge pull request #6913 from samuele3hu/v3_fix

Update lua-template and lua-empty-test for replacing bgMusicPath