CPack: Ensure CPACK_PACKAGE_DIRECTORY is an absolute path
Tested by creating a project, and running:
cpack -B test --config CPackConfig.cmake -> creates the package in ${PWD}/test
cpack -B /test --config CPackConfig.cmake -> creates the package in /test
cpack -D CPACK_PACKAGE_DIRECTORY=test --config CPackConfig.cmake -> creates the package in ${PWD}/test
cpack -D CPACK_PACKAGE_DIRECTORY=/test --config CPackConfig.cmake -> creates the package in /test
Fixes: #18133 (closed), #19412 (closed)
Edited by Brad King