qmake generates paths that contain colons; Since microsoft operating systems have paths with the syntax drive:path the colon is interpreted by make as a separator instead of being part of the path.

The problem is either in your version of make(because it doesn't interpret that colon as expected) or in qmake because it generates a bad Makefile.

It's strange that you are using mingw which is said to be supported by open source Qt.

Maybe you should try with make from MSYS but still I don't understand why it doesn't work with mingw32-make.