So the build script can unconditionally call
export QTC_BUILD=foo
export QTC_SOURCE=bar
qmake -r QTC_PREFIX=/baz CONFIG+=release
make docs
make install
make install_docs

Change-Id: I77bf458b980eb45896d02df5a2c5c0cdc28749d1
Reviewed-by: Christiaan Janssen <christiaan.janssen@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>