Optimize away a fs::metadata call.

[sunfishcode]

This also eliminates a use of a Path convenience function, in support
of #80741, refactoring std::path to focus on pure data structures and
algorithms.

[rust-highfive]

r? @davidtwco

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[davidtwco]

LGTM

[davidtwco]

@bors r+ rollup=never

[bors]

📌 Commit 68338bc has been approved by davidtwco

[bors]

⌛ Testing commit 68338bc with merge 76f7b4322965758d5522df089f1003dcdc4f9e82...

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

Build completed successfully in 0:00:46
+ /scripts/validate-toolstate.sh
Cloning into 'rust-toolstate'...
<Nothing changed>
error: book maintainer @carols10cents is not assignable in the rust-lang/rust repo

  To be assignable, a person needs to be explicitly listed as a
  collaborator in the repository settings. The simple way to
  fix this is to ask someone with 'admin' privileges on the repo
  to add the person or whole team as a collaborator with 'read'
  privileges. Those privileges don't grant any extra permissions
  so it's safe to apply them.
The build will fail due to this.

[bors]

💔 Test failed - checks-actions

[pietroalbini]

@bors retry whoops my fault, sorry

[bors]

⌛ Testing commit 68338bc with merge d7769b9...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing d7769b9 to master...