build with Clang for Valgrind bots (take 2)

I had enough trouble merging that I've written a new CL.

This CL switches the Valgrind bots to Clang and resorts jobs.json.

Looks like we need to go back to limiting to SSE 4.1 when building with
Clang.  (We're much more aggressive about using AVX+ with Clang than we
were GCC.)

Change-Id: Ifbd3126a6ceb9b1c5ed0cf676d0f80d5457fce7e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/255537
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Ben Wagner aka dogben <benjaminwagner@google.com>
2 files changed