Add PATH/LD_LIBRARY_PATH to qrcAlias invocation

Summary: Build fails to generate binary resource (breeze-icons.rcc) by default. The proposed patch fixes this by adding the QtCore directory to the qrcAlias command invocation.

Test Plan:

1. In root of breeze-icons project generate the project using CMake with install prefix set
2. The resultant makefiles or .vcxproj files should have PATH=<path to qt core> (on Windows) and LD_LIBRARY_PATH=<path to qt core> (on Unix)
3. Build the install target
4. Verify that breeze-icons.rcc was successfully copied to <install prefix>/bin/data/icons/breeze
5. Same as 3 but for breeze-icons-dark.rcc

Note: it must be tested when Qt is not already in the PATH or LD_LIBRARY_PATH

Reviewers: VDG, ndavis

Reviewed By: VDG, ndavis

Subscribers: kde-frameworks-devel, VDG

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D24477