Pass `--no-gpg-sign` on toolchain cherry-picks

Passing `--no-gpg-sign` prevents signing on a user's computer from
interfering with the final hash value used in a compiler, if we are
cherry-picking changes into it.

Bug: None
Change-Id: Idab6ba256682153f2f9dc2f228b0a744dadbb254
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8267586
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Claudio DeSouza <cdesouza@chromium.org>
Reviewed-by: Devon Loehr <dloehr@google.com>
Cr-Commit-Position: refs/heads/main@{#1682159}
NOKEYCHECK=True
GitOrigin-RevId: 795e40402b356e24d2c9369712645a1f9767b255