Revert "Fix installation of packages without architecture field"

This reverts commit 13637ddfaf473fa5fd67264da9f38841eeed7401.

The changes in commit 58e7276b69be105735eccb3c18c2b28d3a2ec2e5 were
intentional, supported here meant (although the commit did not
document this properly) that the non-compliant package can still be
installed, although --force-architecture is now required.

src/processarc.c

@@ -282,8 +282,7 @@ void process_archive(const char *filename) {
     return;
   }
 
-  if (strcmp(pkg->available.arch, "") &&
-      strcmp(pkg->available.arch, "all") &&
+  if (strcmp(pkg->available.arch, "all") &&
       strcmp(pkg->available.arch, native_arch))
     forcibleerr(fc_architecture,
                 _("package architecture (%s) does not match system (%s)"),