Allow for Building on Linux with Dark Haxx™

[Neubulae]

What I've done is simply translating the batch commands to their sh equivalents, a tedious task that I'd never get my hands on manually, thx Copilot!
This is a very primitive attempt of building The Archive on Linux(and possibly other Unix-like OSes, provided .NET SDK, and coreutils-or-equivalent are installed). As changes to Windows batchfiles are included, this "patch" needs to be tested on Windows to see whether the formatting messes with VS.
As such, the process is no longer automated by VS, dependency resolution(a la dotnet restore) has to be done manually with each submodule before building, the following procedure is concluded:

1. run dotnet restore --force /property:Configuration=R_xx(with R_xx your desired modloader) for TheArchive_Core, TheArchive_IL2CPP, and TheArchive_MONO. No need for BuildHelper it seems, as it helps itself out. Pretty helpful BuildHelper!
2. then run dotnet build --configuration R_xx under the root. Again with R_xx your desired modloader.
3. Profit??
   I have tested the produced binary and it seems to be running well on my machine, I hope anybody out there could help with this PR, XOXO <3

[GreatWyrm]

Just tried it out on my Linux system, can confirm it builds correctly! Thanks for making it work, I attempted it before and it was a real headache.