build_all_repos: Don't quote variables that can be empty

[stdweird]

Needed for EL5 builds.

[stdweird]

@jrha codeclimate boo. needed for el5 builds, seems ok on el6 and el7. i'm retesting now.

[jrha]

The more I think about the more I prefer wrapping the calls to yum in a function.

[stdweird]

@jrha magic comments don't seem to work

[jrha]

I got the magic number wrong... it should be 2086.

[stdweird]

@jrha 🥗

[jrha]

b~a~uild_all_repos: return non-zero value when perl version is way too old