[libc++][CI] Updates GCC to version 12.

Reviewed By: ldionne, philnik, #libc, #libc_abi

Differential Revision: https://reviews.llvm.org/D126667

NOKEYCHECK=True
GitOrigin-RevId: eb12ad9d7ff64398add1a9cc84e56cc20aed09f8
1 file changed