bug#52913: 0ad only builds fine with a specific version of mozjs

[Jesse Gibbons <jgibbons2357@gmail.com>]

 > What would be the best way to fix this?
 >  - keep a mozjs-78.6 package around just for 0ad
 >  - patch 0ad to fix the compatibility issues with mozjs 78.15
 >  - use the mozjs version bundled in the 0ad sources
 >
 > WDYT?

Keeping mozjs-78.6 just for 0ad will probably make things harder later 
on because it's another package to maintain and users likely won't be 
able install 0ad and icecat/icedove in the same profile. I suppose users 
can always use `-P /path/to/0ad-profile` when installing or updating 0ad.

I'm thinking using the bundled mozjs is perhaps the best option, though 
it isn't particularly guixy, because I expect most users would want the 
0ad packaged by guix to be compatible with other 0ad builds in the wild. 
However, I think it would be useful to fix compatibility issues with 
mozjs 78.15 so interested contributors can tell upstream if guix's 
current minor version breaks the expected deterministic behaviors 
described in the error.

Another option would be to keep mozjs-78.6 for 0ad and patch it so 
interested users can test updated mozjs using 
`--with-input=mozjs=mozjs`. It isn't very difficult to modify a list of 
packages to use a specific mozjs in a manifest or home configuration, 
right? Though I guess interested contributors could always add the patch 
themselves just as easily...

Anyway, that's my two cents.