Avert MSRV breakage in WASM & no-std builds. #6511

Job	Run time
Latest build on ubuntu-latest	1m 48s
Check ZFuture build on Linux	24s
Latest build on windows-latest	4m 43s
Check ZFuture build on macOS	47s
Latest build on macOS-latest	2m 45s
Check ZFuture build on Windows	1m 47s
Test no-Orchard on Linux	4m 33s
Test Orchard on Linux	6m 25s
Test no-Orchard on macOS	5m 42s
Test NU7 on Linux	6m 35s
Test Orchard on macOS	11m 8s
Test no-Orchard on Windows	8m 32s
Test Orchard on Windows	12m 24s
Test NU7 on Windows	12m 59s
Slow Test Orchard on Linux	4m 18s
Bitrot check	1m 15s
Slow Test NU7 on Linux	4m 18s
Build target wasm32-wasi	1m 0s
Build target thumbv7em-none-eabihf	36s
Clippy (MSRV)	1m 16s
Clippy (beta)	14s
Code coverage	1h 32m 15s
Intra-doc links	2m 13s
Rustfmt	14s
protobuf consistency	1m 3s
UUID validity	3s
Required status checks have passed	1s
	3h 9m 18s

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