Print build error messages for compile workflow

[bcat]

Use the userspace-compile -p flag to show verbose errors when userspace builds via GitHub Actions fail.

Failure log before (no idea what I did wrong): https://github.com/bcat/qmk_userspace/actions/runs/19383283478/job/55465913714

Failure log after (oops, forgot ENCODER_MAP_ENABLE): https://github.com/bcat/qmk_userspace/actions/runs/19383530540/job/55466590376

[zvecr]

As the current use case is to use these steps unpinned, and the qmk_firmware fork could be "old", we probably need this to be backwards compatible.

Something like this should work:

Suggested change

	qmk userspace-compile -e DUMP_CI_METADATA=yes -p || touch .failed
	if qmk userspace-compile --help | grep -q "print-failures"; then
	EXTRA_ARGS="-p"
	fi
	qmk userspace-compile -e DUMP_CI_METADATA=yes $EXTRA_ARGS || touch .failed

[zvecr]

Closed in favour of #14.