running make install from within tests/gpgscm will install gpgscm in the $PREFIX.
however, gpgscm isn't useful without some of init.scm, repl.scm lib.scm, ffi.scm, etc.
It tends to fail with messages like:
Could not read init.scm: No such file or directory. Consider using GPGSCM_PATH to specify the location of the Scheme library. Error initializing gpgscm: No such file or directory.
So if we're going to ship gpgscm as a binary, we should also ship it with the standard initialization .scm files, and they should be placed in some standard place that gpgscm can find them.
Otherwise, we shouldn't bother installing gpgscm at all, and just leave it as an internal development utility.