There are formulae that use resource blocks for stuff that is needed in
test blocks. If a resource is a `.zip` archive, one needs `unzip`
utility in `PATH` to extract it, but its only available at build-time,
so one observes an error like that for example:
```
==> brew test psftools --verbose
Testing psftools
==> Downloading https://www.zone38.net/font/pc8x8.zip
Already downloaded: /github/home/.cache/Homebrew/downloads/ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip
==> Verifying ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip checksum
unzip -o /github/home/.cache/Homebrew/downloads/ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip -d /tmp/d20200304-21389-ui0wr0
Error: psftools: failed
undefined method `shelljoin' for nil:NilClass
```
Of course this issue affects Linux the most, because of higher
probability that the system lacks `unzip` for example.
With this commit, all resource guessed dependencies should be available
at build and test time.
59ce122e90