On a fresh pull of core-updates-frozen it seems the --dry-run option has stopped doing anything.
My test case is guix build --dry-run qtwebkit (no subs currently), but guix immediately starts compiling qtwebkit. I can't be sure when it started, but my most recent pull was from a41f93c39d03143ce9007ad278a04fa30498bc0b to 7e8e07033d2a6b0ecef566a05084c534c774cd4a It may have started before that though.
