[FIX] checkers: Don't faill when variables.sh contains comments

Currently, all lines of the `variables.sh` file should follow the
pattern:
EXPORT varname=value

However, that pattern disallows lines that are just comments, e.g.
starting with `#`.

This commits allows also comments as valid lines.
Status Job ID Name Coverage
  Test
passed #351531
lint
test_install

00:00:18