gitlab-ci: download gfortran as part of the CI job

12 jobs for !765 with ci-macos
merge request
Name Stage Failure
build:macos-plain Build
WARNING: build/superbuild/superbuild_testing_trampoline.cmake: no matching files 
WARNING: build/tests/: no matching files
WARNING: build/CTestCustom*.cmake: no matching files
WARNING: build/CTestTestfile.cmake: no matching files
WARNING: build/superbuild/CTestTestfile.cmake: no matching files
build/Testing/: found 10 matching files and directories

WARNING: build/DartConfiguration.tcl: no matching files
Uploading artifacts as "archive" to coordinator... ok
id=5187151 responseStatus=201 Created token=VeoUA13N
ERROR: Job failed: exit status 1