cmov

cpufeatures: add compile time fallback for unsupported targets and target features #698

Job	Run time
build (stable, thumbv7em-none-eabi)	12s
build (1.85.0, thumbv7em-none-eabi)	19s
build (1.85.0, wasm32-unknown-unknown)	17s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.85.0)	21s
minimal-versions / minimal-versions	26s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.85.0, sudo apt update && sudo apt install gcc-mult...	36s
test (x86_64-pc-windows-msvc, windows-latest, 1.85.0)	30s
build (stable, wasm32-unknown-unknown)	16s
cross (aarch64-unknown-linux-gnu, 1.85.0)	39s
test (x86_64-apple-darwin, macos-latest, 1.85.0)	20s
cross (powerpc-unknown-linux-gnu, 1.85.0)	33s
cross (aarch64-unknown-linux-gnu, stable)	40s
cross (powerpc-unknown-linux-gnu, stable)	32s
	5m 41s

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