cpubits: add 64-bit override for ARMv7 #62

Job	Run time
test-cross (powerpc-unknown-linux-gnu)	1m 9s
test-wasm (stable)	16s
test-cross (armv7-unknown-linux-gnueabi)	1m 9s
test-wasm (1.85)	22s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.85.0)	18s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.85.0, sudo apt update && sudo apt install gcc-mult...	32s
test (x86_64-apple-darwin, macos-latest, 1.85.0)	21s
test (x86_64-pc-windows-msvc, windows-latest, 1.85.0)	32s
	4m 39s

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