Format libstd/sys with rustfmt

This commit applies rustfmt with rust-lang/rust's default settings to
files in src/libstd/sys *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/sys -name '*.rs' \
        | xargs rustfmt --edition=2018 --unstable-features --skip-children
    $ rg libstd/sys 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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libstd/sys/unix/thread_local.rs b/src/libstd/sys/unix/thread_local.rs
index ac615b76b36..2c5b94b1e61 100644
--- a/src/libstd/sys/unix/thread_local.rs
+++ b/src/libstd/sys/unix/thread_local.rs
@@ -5,7 +5,7 @@ use crate::mem;
 pub type Key = libc::pthread_key_t;
 
 #[inline]
-pub unsafe fn create(dtor: Option<unsafe extern fn(*mut u8)>) -> Key {
+pub unsafe fn create(dtor: Option<unsafe extern "C" fn(*mut u8)>) -> Key {
     let mut key = 0;
     assert_eq!(libc::pthread_key_create(&mut key, mem::transmute(dtor)), 0);
     key