Avoid syncing pantry if the cache provides the pkgspec, even if it's old

[felipecrs]

This is a continuation of:

• fix: docker image not building lowlighter/metrics#1724 (comment)

Please read it, all my reasoning is there.

[felipecrs]

According to @mxcl pkgx^2 already functions like this.

[mxcl]

We only sync (with ^2) if we cannot find a requested program or dependency. So yes, should work this way already.

pkgx^1 would also sync if the pantry was old, though I decided for ^2 that this was not great UX for a “runner” which should always aim to be as fast as possible without unexpected bumps.

[felipecrs]

Completely agreed!