add dumpJIT() to disassemble

This is yet another debug tool there to help me on
machines that I can't profile with perf or vtune.

Reorganize debug hooks in SkVMBlitter a little.

Disabled on Windows... no llvm-mc, popen, or memmem.

Change-Id: I56d01a6df494aae126c66b9558f57b7449124c95
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/264478
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
3 files changed