Rollup merge of #66818 - dtolnay:fmt1, r=Dylan-DPC

Format libstd/os with rustfmt

(Same strategy as #66691.)

This commit applies rustfmt with rust-lang/rust's default settings to files in src/libstd/os *that are not involved in any currently open PR* to minimize merge conflicts. The list of files involved in open PRs was determined by querying GitHub's GraphQL API [with this script](https://gist.github.com/dtolnay/aa9c34993dc051a4f344d1b10e4487e8).

With the list of files from the script in outstanding_files, the relevant commands were:

    $ find src/libstd/os -name '*.rs' \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ rg libstd/os outstanding_files | xargs git checkout --

Repeating this process several months apart should get us coverage of most of the rest of the files.

To confirm no funny business:

    $ git checkout $THIS_COMMIT^
    $ git show --pretty= --name-only $THIS_COMMIT \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ git diff $THIS_COMMIT  # there should be no difference

0 files changed, 0 insertions, 0 deletions