Fix EMSCRIPTEN root path search in CMake toolchain file.
Fix tools/validate_asmjs.py to not throw if SPIDERMONKEY_ENGINE is not properly set.
Fix other.test_cmake to not fail on Ninja generator if EM_BUILD_VERBOSE=3
Fix test other.test_cmake to build after updates to CMake system.
Clean up extra littering includes in Bullet build file to avoid noise. Upstreaming progress at https://github.com/bulletphysics/bullet3/pull/197