Switch almost all of Pal to Rusty error handling.

src/header/sys_file/mod.rs

@@ -1,6 +1,9 @@
 //! sys/file.h implementation
 
-use crate::platform::{types::*, Pal, Sys};
+use crate::{
+    error::ResultExt,
+    platform::{types::*, Pal, Sys},
+};
 
 pub const LOCK_SH: usize = 1;
 pub const LOCK_EX: usize = 2;
@@ -13,5 +16,5 @@ pub const L_XTND: usize = 2;
 
 #[no_mangle]
 pub extern "C" fn flock(fd: c_int, operation: c_int) -> c_int {
-    Sys::flock(fd, operation)
+    Sys::flock(fd, operation).map(|()| 0).or_minus_one_errno()
 }