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, 2 insertions, 6 deletions

diff --git a/src/libstd/sys/hermit/thread_local.rs b/src/libstd/sys/hermit/thread_local.rs
index 268fb770eae..ba967c7676c 100644
--- a/src/libstd/sys/hermit/thread_local.rs
+++ b/src/libstd/sys/hermit/thread_local.rs
@@ -7,7 +7,7 @@ use crate::sys_common::mutex::Mutex;
 
 pub type Key = usize;
 
-type Dtor = unsafe extern fn(*mut u8);
+type Dtor = unsafe extern "C" fn(*mut u8);
 
 static NEXT_KEY: AtomicUsize = AtomicUsize::new(0);
 
@@ -41,11 +41,7 @@ pub unsafe fn create(dtor: Option<Dtor>) -> Key {
 
 #[inline]
 pub unsafe fn get(key: Key) -> *mut u8 {
-    if let Some(&entry) = locals().get(&key) {
-        entry
-    } else {
-        ptr::null_mut()
-    }
+    if let Some(&entry) = locals().get(&key) { entry } else { ptr::null_mut() }
 }
 
 #[inline]