Add rustc_codegen_gcc repo under automation

[Kobzol]

Repo: https://github.com/rust-lang/rustc_codegen_gcc

CC @antoyo

Extracted from GH:

org = "rust-lang"
name = "rustc_codegen_gcc"
description = "libgccjit AOT codegen for rustc"
bots = []

[access.teams]
security = "pull"
compiler = "maintain"

[access.individuals]
estebank = "maintain"
Aaron1011 = "maintain"
pnkfelix = "maintain"
eddyb = "maintain"
petrochenkov = "maintain"
matthewjasper = "maintain"
cjgillot = "maintain"
pietroalbini = "admin"
jackh726 = "maintain"
rust-lang-owner = "admin"
wesleywiser = "maintain"
rylev = "admin"
davidtwco = "maintain"
michaelwoerister = "maintain"
oli-obk = "maintain"
lcnr = "maintain"
compiler-errors = "maintain"
nagisa = "maintain"
jdno = "admin"
antoyo = "write"
Mark-Simulacrum = "admin"
badboy = "admin"

[GuillaumeGomez]

What exactly does it add?

[Kobzol]

It doesn't really add anything, I just want to move the repo under automation. Currently, most of our repos are managed manually, and I'm now doing a sweep across these and moving them under team one by one :)

[GuillaumeGomez]

Nice! Glad to see more automation coming in. :)