Enable use of MODULE_PATH and other built-ins in update/download and prepare/extract

Make it work for tools/clang+llvm/* modules

added 1 deleted label

assigned to @dreher

Merged !465 (merged) as a hotfix for issues resulting from this feature missing

mentioned in merge request !472 (merged)

mentioned in commit 4a2f06aa

closed with merge request !472 (merged)

changed milestone to %Release 23.01.2.0

added feature-request label