Merge pull request #450 from zcash/no_std_ci #3330

Job	Run time
Bitrot check	2m 10s
Book tests	16s
Latest build on ubuntu-latest	48s
Build target wasm32-wasi	1m 33s
Latest build on windows-latest	2m 23s
Build target thumbv7em-none-eabihf	1m 26s
Code coverage	9m 3s
Latest build on macOS-latest	45s
Test on ubuntu-latest	10m 7s
Test on windows-latest	12m 0s
Test on macOS-latest	9m 32s
Intra-doc links	2m 27s
Rustfmt	15s
	52m 45s

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