Fix compile of `arbitrary` feature. (#505) #42

Job	Run time
Linux (1.56.0)	3m 22s
Linux (stable)	41s
Linux (beta)	32s
Linux (nightly)	30s
Linux (--features serde, 1.56.0)	3m 7s
Linux (--features serde, stable)	26s
Linux (--features serde, beta)	44s
Linux (--features serde, nightly)	33s
Linux (--no-default-features --features libm, 1.56.0)	2m 51s
Linux (--no-default-features --features libm, stable)	26s
Linux (--no-default-features --features libm, beta)	36s
Linux (--no-default-features --features libm, nightly)	29s
Linux (stable, --features mint)	30s
Linux (stable, --features bytemuck)	43s
Linux (stable, --features arbitrary)	24s
Linux (nightly, --features unstable)	26s
Linux (nightly, --features unstable,serde)	34s
Result	1s
	16m 55s

Provide feedback