- Add `-msimd128` to flags to actually enable WebAssembly SIMD
when performing SIMD detection. It's currently required in
addition to `-msse*` / `-mfpu=neon` flags which only perform
translation of corresponding intrinsics to Wasm SIMD ones.
See a discussion at emscripten-core/emscripten#12714 for
automating this and making easier in the future.
- Remove compilation branch that prevented definitions of
`WEBP_USE_SSE` and `WEBP_USE_NEON` on Emscripten even when
SIMD support was detected at compile-time.
- Add an implementation of `VP8GetCPUInfo` for Emscripten which
uses static `WEBP_USE_*` flags to determine if a corresponding
SIMD instruction is supported. This is because Wasm doesn't
have proper feature detection (yet) and requires making separate
build for SIMD version anyway.
Change-Id: I77592081b91fd0e4cbc9242f5600ce905184f506