Add homebrew-binary to search
Add comment to superenv ENV to note trailing if
Remove ARCHFLAGS fixme from Python dependency

This will be handled by env/superenv, not Python.
Move perforce brews to homebrew-binary

Closes #19774.
readline: add Darwin 13 as a build target

Closes #21625.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>