[Interest] qmake: mkspec linux-g++ not found

[Jason H]

I built Qt from sources, did a make install, then blew away the source directory. 
I went into my project dir, did qmake and got that error.
I looked in /usr/local/Qt-5.4.1/mkspecs and there were the proper files there.

Then I un-blew away the source dir (cautious me, I did a move) and it all worked.
There seems to be a dependency on /data/qt/src/qtbase/bin/qt.conf 

How can I blow away the source dirs and still have it work?

Thanks