Fixes <https://bugs.gnu.org/47569>.
Previously the wrapper's XDG_DATA_DIRS would contain any input that had
a /share sub-directory, which is usually all build-time inputs.
* guix/build/qt-build-system.scm (variables-for-wrapping)[collect-sub-dirs]:
Add 'selectors' parameter and honor it. Change caller to handle
selectors. Add selectors for /share.
* guix/build/qt-build-system.scm (check-setup): New function.
(%standard-phases): Add as new phase `check-setup before `check.
* doc/guix.texi (Build System)[qt-build-system]: Describe the new phase.