go/build: allow io/fs to depend on time
go/build: allow io/fs to depend on time

In preparation for moving os.FileInfo into io/fs.
Also keep syscall from depending on io again.
We want to keep them separated, in case io ever
needs to start depending on time.

For #41190.

Change-Id: I98350fa03accf4a20c75ddebb0e961aa1ccccd2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/243905
Trust: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Run-TryBot: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

CAFxX/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,CAFxX/go,golang/go,cloudflare/go,CAFxX/go,cloudflare/go,cloudflare/go,nawawi/go,golang/go,CAFxX/go,cloudflare/go,CAFxX/go,cloudflare/go,nawawi/go,golang/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,CAFxX/go