added emsdk and build script #321

Job	Run time
test-win (windows-2019, static_build)	4m 3s
test-win (windows-2019, shared_build)	2m 58s
test-unix (ubuntu-20.04, static_build)	2m 33s
test-win (windows-2022, static_build)	5m 25s
test-wasm (3.1.45)	16m 54s
test-win (windows-2022, shared_build)	5m 0s
test-unix (ubuntu-20.04, shared_build)	1m 18s
test-unix (ubuntu-22.04, static_build)	2m 26s
test-unix (ubuntu-22.04, shared_build)	1m 27s
test-unix (macos-11, static_build)	4m 6s
test-unix (macos-11, shared_build)	4m 3s
test-unix (macos-12, static_build)	3m 23s
test-unix (macos-12, shared_build)	2m 49s
	56m 25s

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