Revert "Makefile: refactor environment check"
Revert "Makefile: refactor environment check"

This was breaking the build because the AWS cred check doesn't work when
run in the pipeline. Reverting this while we work out a fix for this.

This reverts commit e1a9a229ea543a369136d4553b41b7ebd1cf4d6c.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf