Backport build.rs fixes to 2.x. #1725

Job	Run time
Check Cross-Compilation on Rust nightly (nightly)	47s
Check Cross-Compilation (stable)	39s
Check Cross-Compilation (beta)	51s
Check Cross-Compilation on Rust nightly on Windows (nightly)	45s
Check Cross-Compilation on Windows (stable)	54s
Fuzz Targets	53s
Check Cross-Compilation on Windows (beta)	52s
Rustfmt	6s
Test (stable)	10s
Test linux-raw support (ubuntu)	30s
Test (windows-latest)	9s
Test (msrv)	2m 21s
Test on Musl (ubuntu)	26s
Test linux-raw support (ubuntu-20.04)	30s
Test (windows-2019)	6s
Test (macos-latest)	13s
Test (macos-11)	1s
Test with Rust nightly (ubuntu)	31s
Test (beta)	17s
Test with Rust nightly (windows)	47s
Test (ubuntu-20.04)	11s
Test (aarch64-ubuntu)	21s
	12m 20s

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