also properly prepare templating with --job and --regtest

This patch fixes an issue when templating constants are used in easyconfigs, and the build are submitted via `--job` or run using `--regtest --sequential`.

Issues like below occur:

```
main.EasyConfig WARNING Unable to resolve template value %(namelower)s-%(version)s.tar.gz with dict {'versionsuffix': '', 'versionprefix': ''}
...
main.ConfigureMake DEBUG Trying to download file %(namelower)s-%(version)s.tar.gz from http://ftpmirror.gnu.org/gperf/%(namelower)s-%(version)s.tar.gz
```

This is very probably an indication that some cleanup is in order since the same lines of code have to be included in multiple locations, but it fixes the issue for now.
Cleanup should be done as a part of a follow-up issue.