Generate Makefiles instead of Xcode projects on macOS

If you call qmake of the prebuilt binaries of Qt, it produces XCode project files (xxx.xcodeproj) instead of make files. You can create regular make files with this commands:

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

If you want to create make files per default, you can tell qmake by executing the following commands

cd $QTDIR/mkspecs
rm default

ln -s macx-g++ default