Rust

Fix performance on MacOS #126

Job	Run time
build-unix (stable, ubuntu)	13s
build-unix (stable, macos)	19s
build-windows (i686, msvc, stable)	1m 33s
build-unix (beta, ubuntu)	20s
build-windows (i686, msvc, beta)	56s
build-unix (beta, macos)	18s
build-windows (i686, msvc, nightly)	46s
build-unix (nightly, ubuntu)	19s
build-windows (x86_64, gnu, stable)	4m 47s
build-unix (nightly, macos)	19s
build-windows (x86_64, gnu, beta)	2m 39s
build-windows (x86_64, gnu, nightly)	2m 37s
build-windows (x86_64, msvc, stable)	53s
build-windows (x86_64, msvc, beta)	55s
build-windows (x86_64, msvc, nightly)	55s
build-windows (aarch64, msvc, stable)	1m 21s
build-windows (aarch64, msvc, beta)	47s
build-windows (aarch64, msvc, nightly)	39s
	20m 36s

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