PyPy 2.1

Closes #21587.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Set ARCHFLAGS without ppc support

Closes #20633.
rdiff-backup: ARCHFLAGS handled by :python
add comment to ENV
ENV sets ARCHFLAGS for universal
ENV sets ARCHFLAGS in m32 and m64
debug comments
Add comment to superenv ENV to note trailing if
Document superenv HOMEBREW_CCFG flags