Fix experimental_simd CanvasKit build.

Although it appeared that the experimental_simd CanvasKit build was
working, the build was not producing actual wasm SIMD operations. This
CL fixes that issue by changing the build arguments.

This issue also fixes an incorrect type issue with the SkVx wasm SIMD
implementation.

Bug: skia:10453
Change-Id: If26f84b09e4d84df36be589245878c821972dffc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302669
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
2 files changed