setup: use elm-format-0.18 in mkFrontend check phase.
setup: use elm-format-0.18 in mkFrontend check phase.

La0/mozilla-relengapi,garbas/mozilla-releng-services,srfraser/services,garbas/mozilla-releng-services,lundjordan/services,srfraser/services,mozilla-releng/services,lundjordan/services,srfraser/services,lundjordan/services,mozilla-releng/services,andrei987/services,mozilla-releng/services,La0/mozilla-relengapi,La0/mozilla-relengapi,srfraser/services,garbas/mozilla-releng-services,La0/mozilla-relengapi,mozilla-releng/services,garbas/mozilla-releng-services,andrei987/services,lundjordan/services,andrei987/services,andrei987/services