Fix and cleanup the SM91 build, fixes #6676.

Add a new patch written by s0600204, replacing the use of distutils with sysconfig in the setup of the bundled virtualenv in SpiderMonkey.
Add a patch which is a portion of https://phabricator.services.mozilla.com/D130410, fixing upstream's bug 1739486 on Fedora.

This fixes build issues on recent Debian and Fedora. This is consistent with upstream's upcoming changes in ESR102 following the deprecation of distutils.

This cleans up some old SM patches; renames the r27442 unicode patch; moves a Python-related environment variable inside build.sh; fixes indentation and EOL properties.

Differential Revision: https://code.wildfiregames.com/D4893