add emscripten builds, with and without SIMD

These build, and hit each side of __wasm_simd128__.
I can disassemble the wasm and see v128 used where appropriate:

    ~/skcms (emcc↑1|✔) $ wasm-objdump -d out/emscripten/skcms.o | grep -q v128 && echo ok || echo no
    ~/skcms (emcc↑1|✔) $ wasm-objdump -d out/emscripten.simd/skcms.o | grep -q v128 && echo ok || echo no

I should note that in order to build the .simd version,
I had to follow these directions to get a bleeding-edge toolchain:

Setting exe=.html creates some handy html/js/wasm files as
the output that you can serve up locally (python -m SimpleHTTPServer)
and run.  Currently failing due to filesystem IO, but it's a start.

    expect(load_file(filename, &buf, &len)) failed at tests.c:615

Change-Id: Ib9473584b43ec35ea2bb81d9765c6814b5084e89
Reviewed-by: Mike Klein <>
Commit-Queue: Mike Klein <>
3 files changed