Option --only-tarball should not validate the ArchiveURL

[sebasguts]

Currently, the (undocumented) --only-tarball checks the ArchiveURL:

release --only-tarball
Extracting information from PackageInfo.g...
Package Metapackage 0.1
ERROR: The ArchiveURL has unexpected value 'https://sebasguts.github.io/MetaPackageMetaPackage-0.1'

[fingolfin]

I am not sure about this. Package validation should always happen, even if you just want to create tarball.

From the sample message, I assume this is for meta packages. In that case, it seems to me that the better solution would be to teach release about meta packages. But for now, I am not even sure why there is a problem; the output simply looks like there is a genuine bug in the ArchiveURL.