Improve Gentoo ebuild #215

Job	Run time
Clippy (ubuntu-latest)	25s
Build (x86_64-unknown-linux-gnu)	2m 24s
Rustfmt	25s
Clippy (windows-latest)	3m 0s
Build (i686-unknown-linux-gnu)	2m 32s
Clippy (windows-latest)	3m 1s
Build (aarch64-unknown-linux-gnu)	2m 40s
Clippy (macos-latest)	1m 2s
Build (armv7-unknown-linux-gnueabihf)	2m 34s
Build (x86_64-pc-windows-msvc)	4m 36s
Build (i686-pc-windows-msvc)	4m 52s
Build (x86_64-pc-windows-msvc)	7m 15s
Release on GitHub	0s
Release on packagecloud.io	0s
Release on Gentoo GURU	0s
Release on Windows Package Manager	0s
Release on Arch User Repository	0s
Release on Chocolatey	0s
Release on Homebrew	0s
	34m 46s

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