invisible universal variant and merger_must_run_binaries

[Ken Cunningham]

The good news is I currently only see 7 ports that set "merger_must_run_binaries" grepping the repo.

If we don't have to add too many more to the list as we explore more universal builds, then perhaps we can fix these to not need it, and solve our problem cleanly that way.

Several are core ports, though.

icu, readline, libgpg-error are probably the three biggest to fix, if possible.

Ken