Revert "move conditions for JIT into SkVM.h"

This reverts commit 166cd52cee64fb59a1c8daad379feca2e18d723a.

Reason for revert: iOS simulator was on unintentionally

Original change's description:
> move conditions for JIT into SkVM.h
> 
> This makes it easier to keep in sync with the implementation in
> SkVM.cpp, and it's easier to handle here once than in each build system.
> 
> Change-Id: I429f90cfc16f35a0d7e0b0fde176bc013aa7db18
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/310263
> Commit-Queue: Mike Klein <mtklein@google.com>
> Commit-Queue: Herb Derby <herb@google.com>
> Auto-Submit: Mike Klein <mtklein@google.com>
> Reviewed-by: Herb Derby <herb@google.com>

TBR=mtklein@google.com,herb@google.com,reed@google.com

Change-Id: I1ae283be09906603c207079cbf6f1e296a4835f8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/310462
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
3 files changed