.gitlab-ci.yml: Pin ghc version to fix build
As there is a new release 8.4.3 of ghc and no resolver is available, this pins last known working version 8.4.2 to fix the build errors.
Closes #194 (closed)
As there is a new release 8.4.3 of ghc and no resolver is available, this pins last known working version 8.4.2 to fix the build errors.
Closes #194 (closed)