scons: Add version 3.0.2

"SCons release 3.0.2 now available from the download page at
SourceForge. This release should be used instead of 3.0.1. This release
fixes several issues. This release supports Python versions 2.7.* as
well as 3.5+." [0]

Details can be found in the changelog [1].

I'll update the default after running additional tests.

[0]: https://scons.org/scons-302-is-available.html
[1]: https://raw.githubusercontent.com/SConsProject/scons/rel_3.0.2/src/CHANGES.txt