Remove .skvm generation support from skslc.

SkVM is being removed; we no longer need to compile golden outputs
for its code generator.

Change-Id: I4ae556a77002843d0eda7a1917fbc5b07440b5b0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/687638
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
93 files changed