Use OS temp directory instead of CARGO_TARGET_TMPDIR in bindgen tests #2982

Job	Run time
check (stable, x86_64-pc-windows-msvc, x86_64-pc-windows-msvc)	19m 54s
check (stable, x86_64-pc-windows-msvc, x86_64-pc-windows-msvc)	12m 27s
check (nightly, x86_64-pc-windows-msvc, i686-pc-windows-msvc)	20m 54s
check (nightly, x86_64-pc-windows-msvc, i686-pc-windows-msvc)	12m 23s
check (nightly, x86_64-pc-windows-gnu, x86_64-pc-windows-gnu)	24m 36s
check (nightly, x86_64-pc-windows-gnu, x86_64-pc-windows-gnu)	12m 19s
check (stable, x86_64-pc-windows-gnu, i686-pc-windows-gnu)	24m 6s
check (stable, x86_64-pc-windows-gnu, i686-pc-windows-gnu)	12m 26s
check (stable, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	19m 6s
check (stable, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	12m 35s
check (nightly, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	21m 8s
check (nightly, x86_64-pc-windows-msvc, aarch64-pc-windows-msvc, --no-run)	12m 23s
	3h 24m 17s

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