Generate Makefiles instead of Xcode projects on macOS

If you call qmake from the prebuilt binaries of Qt, it produces Xcode project files (xxx.xcodeproj) instead of makefiles. You can create regular makefiles with these commands:

rm -rf hello.xcodeproj
rm Info.plist
 
qmake -spec macx-g++

If you want to create makefiles by default, you can tell qmake by executing the following commands:

cd $QTDIR/mkspecs
rm default

ln -s macx-g++ default