add `__wasilibc_reset_preopens` #53

Job	Run time
Rustfmt	17s
wasi-headers test	0s
Build libc (ubuntu-latest, 10.0.0)	1m 31s
Build libc (macos-latest, 10.0.0)	2m 7s
Build libc (windows-latest, 10.0.0)	3m 25s
Build libc (ubuntu-latest, 16.0.0, x86_64-linux-gnu-ubuntu-18.04)	3m 29s
Build libc (macos-latest, 15.0.7, x86_64-apple-darwin21.0)	4m 4s
Build libc (windows-latest, 16.0.0)	4m 43s
	19m 36s

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