Improve emscripten support #211

Job	Run time
clippy	15s
docs	13s
Rustfmt	10s
Test (ubuntu-latest, 1.70)	24s
Test (ubuntu-latest, stable)	49s
Test (ubuntu-latest, beta)	30s
Test (ubuntu-latest, nightly)	24s
Test (macos-latest, 1.70)	38s
Test (macos-latest, stable)	29s
Test (macos-latest, beta)	31s
Test (macos-latest, nightly)	26s
Test (windows-latest, 1.70)	1m 8s
Test (windows-latest, stable)	1m 26s
Test (windows-latest, beta)	1m 52s
Test (windows-latest, nightly)	1m 4s
Test Cross Compile - aarch64-unknown-linux-gnu	41s
Test Cross Compile - aarch64-apple-ios	22s
Test Cross Compile - arm-unknown-linux-gnueabihf	44s
Test Cross Compile - powerpc-unknown-linux-gnu	47s
Test Cross Compile - s390x-unknown-linux-gnu	28s
Test Cross Compile - x86_64-unknown-linux-musl	44s
Test Cross Compile - aarch64-unknown-linux-musl	41s
Test Cross Compile - x86_64-pc-solaris	33s
Test Cross Compile - x86_64-pc-windows-gnu	1m 10s
Test Cross Compile - x86_64-unknown-netbsd	51s
Test Cross Compile - x86_64-unknown-illumos	33s
success	1s
	17m 54s

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