Added support for building new archives

[bravely-beep]

This does indeed build my new .sbactorpack archive, but it breaks something else - if I include edits to TitleBG.pack in the patch files, it becomes impossible to pick up one-handed swords off the ground. Strangely, this still happens even if the patch files in TitleBG.pack are identical to the originals. I checked, and the TitleBG.pack built by the patcher was identical to the original, so the error has to be in a different file - maybe the RSTB?

[leoetlino]

Hmm, that seems really weird. I can't see anything wrong with your changes...

Have you tried comparing the generated RSTBs?

[bravely-beep]

Turns out I misdiagnosed the issue:

If I don't add a new archive, I get no errors ever, using PR1 and PR2
If I do add a new archive, it obviously doesn't work at all with PR1, and using PR2 causes the picking-up-swords glitch
From now on I'll only use the PR2 build of the patcher
Running the patcher with a new archive, then deleting the new sbactorpack from the built files, will still cause the error
TitleBG doesn't seem to affect anything

[bravely-beep]

Confirmed that the issue is with rstbtool, not the patcher
Should be okay to merge this then