Contract violation building snapshot

[pmatos]

For a snapshot build that doesn't lock (as in #3140) issued with:

$ make snapshot-site CONFIG=$PWD/.github/workflows/site-small.rkt CPUS=4
...
make set-server-config
make[8]: Entering directory '/home/pmatos/dev/racket'
racket/bin/racket -G build/user/config -X racket/collects -A build/user -MCR /home/pmatos/dev/racket/build/zo: -l distro-build/set-server-config build/user/config/config.rktd "/home/pmatos/dev/racket/.github/workflows/site-small.rkt" "default" "" "" "" ""
build-path: contract violation
  expected: (or/c path-for-some-system? path-string? 'up 'same)
  given: #f
  argument position: 1st
  other arguments...:
   "ci-snapshots/20200501-ea43027252"
  context...:
   "/home/pmatos/dev/racket/.github/workflows/site-small.rkt": [running body]
   temp35_0
   for-loop
   run-module-instance!
   do-dynamic-require
   /home/pmatos/dev/racket/build/user/7.7.0.4/pkgs/distro-build-server/config.rkt:233:0: extract-options
   "/home/pmatos/dev/racket/build/user/7.7.0.4/pkgs/distro-build-server/set-server-config.rkt": [running body]
   temp35_0
   for-loop
   run-module-instance!
   perform-require!

I get the above mentioned contract violation.

[pmatos]

My problem here... site-small.rkt defines DISTRO_BUILD_SITE_DEST in

racket/.github/workflows/ci-snapshot.yml

Line 32 in ea43027

DISTRO_BUILD_SITE_DEST: "${{ runner.temp }}/site-dest/"

which I don't do locally, therefore the #f in build-path.

Sorry for the noise.