This is a reland of f1a937f141
Original change's description:
> export SkRuntimeShaderBuilder
>
> ... like we do SkRuntimeEffect.
>
> Change-Id: I024f1716b2f818d24b002213c02fa83d2b271123
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/377757
> Commit-Queue: Mike Klein <mtklein@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
> Auto-Submit: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>
Cq-Include-Trybots: luci.skia.skia.primary:Build-Win-MSVC-x86_64-Release-Shared
Change-Id: I82c440be4ea53e21c6c3d2b6999d832f71563d83
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/377859
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
a950fef9db