Build python with hash-based .pyc files
Build python with hash-based .pyc files

Resetting the file mtimes of the python image invalidates the compiled
cache files, forcing them to be recompiled when they are first imported.
Set SOURCE_DATE_EPOCH to force generation of hash-validated .pyc files
instead of mtime-validated ones.

Because fixing the #! path in .py files invalidates .pyc hashes, do this
before starting the main build rather than at the end.

arachsys/packages,arachsys/packages