Specify a source filename depending on variants?

[Rob Groner]

I'm attempting to install a newer version of ADF using the built-in package.  However, besides using a newer version, I'm also trying to use the intelmpi binary instead of the openmpi binary.

The url_for_version() that exists has openmpi hard-coded in:

    def url_for_version(self, version):

        return "file://{0}/adf/adf{1}.pc64_linux.openmpi.bin.tgz".format(

               os.getcwd(), version)

I tried creating a variant for which MPI was preferred, but that didn't seem to work.  It kept saying it could not fetch.  I also noticed that when I added the binary to my spack mirror, it only notes the package name and version.  So even though there is an a...@2019.303 for openmpi and an a...@2019.303 for intelmpi, there doesn't seem to be a way to make that distinction.

I can just extend the builtin repo version of ADF to solve my own problems, but I had thought to pull-request it back into the baseline.  I don't see how to do that now.