check_clang_diags: fix lints; reformat messaging; change cc

These messages are hard to test for as-written, just use
textwrap.dedent. Also stop cc'ing cjdb on these.

BUG=b:301256174
TEST=Unittests

Change-Id: Id51cec84ecd18ba1846605b585c138c6fcff3e6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/4877572
Tested-by: George Burgess <gbiv@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
2 files changed