build.sh: use gitlab, not anongit
Wellllllllcooooomee to the wooorld of tomoorooooow!
Also, this way we no longer fail on libxcvt which didn't get a membership card to the exclusive anongit club.
A bunch of repos are in different paths or prefixes now, so adjust that as necessary.
Found by @alexhorner in libinput/libinput!775 (comment 1678232)