Revert "package/qt5base: provide "qt.conf" to make "qmake" relocatable"

This reverts commit a2efb84d, as it
causes files to be installed in an invalid location, causing build
failures.

Fixes:

  http://autobuild.buildroot.net/results/a1a9eeb7fec07a2f9f0d05e6c1900ad7cffb6656/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>