remove xbyak

For now, disable the vpmovusdb AVX-512 instruction, using the compound
AVX2 fallback instead.  I need to learn how to encode EVEX prefixes
before we can use that, and it's not very important.

That's everything!  We're fully in control now, and should be able to
run this on any x86-64 Linux or Mac.  And we can relax some of the
defined(SKVM_JIT) guards so that, e.g., we can unit test Assembler even
on all platforms.

Stifle some warnings about ~bool by ~(int)bool.

Would like to enable when is_mac too but can't seem to get past
(bogus?) thread annotation on the bots.  My local Mac is fine. :/

Change-Id: If00bdd97ebd9684ed109933e2fa70c5e6f6ea339
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/222631
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
7 files changed