Add scons

[hadess]

It's used by about 10 separate modules, including the Godot engine.

[TingPing]

As long as somebody agrees to maintain it here.

[eszlari]

Aren't there supposed to be only runtime dependencies here?

flathub/flathub#1479 (comment)

[Erick555]

@eszlari I think that comment was specifically about python2 because if you need it only as build dep then you shouldn't use shared-module which isn't cleaned out. On the other hand if scons will be added to shared-modules with cleanup: [*] then it's ok to reuse it by apps that need it only at build.

[eszlari]

As far as I understand it, shard-modules exists to make sure, modules are built with the exact same options so that flatpak/ostree deduplication works.

[Erick555]

They also exist to reduce maintenance burden. If module is cleaned up then it doesn't need deduplication.

[hsn10]

I would like to have scons too, version 3.0.0. Can be python2 or 3. Version python2 is more used but it will change in near future.