[Cmake] hardcoded prefix for QT_WRAP_UI inputs

[David Thompson]

Hi,

	I have a QT ui file, blah.ui, that I've created using CONFIGURE_FILE so
that some example text gets set to the CMAKE_INSTALL_PREFIX path.
Because the file is generated and placed in my out-of-source build
project_BINARY_DIR, the Makefile complains that there is no rule to make
${project_SOURCE_DIR}/blah.ui. If I try to specify the full path,
${project_BINARY_DIR}/blah.ui, to QT_WRAP_UI the Makefile looks for
${project_SOURCE_DIR}/${project_BINARY_DIR}/blah.ui ... is this a
feature?

		Thanks,
		David