pyside shouldn't try to create uic, rcc and designer copies

This is something we already had to patch out for pyside2. The build system doesn't behave nicely and tries to create rcc and uic copies and fails because it wrongly assumes rcc and uic are installed in /usr/bin.

That was already wrong in our Qt5 package and is not better with pyside6. rcc and uic are now installed in the libexec location.

If the faulty code isn't patched out in sources/pyside-tools/CMakeLists.txt, it creates conflicting binaries in our packages.

build_scripts/platforms/unix.py also needs a change to use the existing rcc and uic executables.