Just to confirm that I can delete the c_code directory and everything will function as normal?
That is correct, yes.
Turns out, you can't remove the docs:
/nim/compiler/commands.nim(61, 16) Error: cannot open file: ../doc/basicopt.txt
For anyone who want to get in with Nim quickly - use Manjaro
Btw, Nim v1.0 has already hit Manjaro Testing branch (only half a day after the release!), and it will be part of the next Stable update.
(Bleeding edge Arch still has Nim v0.18, lol)