fix compilation on uefi targets

Signed-off-by: usamoi <[email protected]>

Author: usamoi

rand_core/src/os.rs

@@ -66,6 +66,14 @@ impl std::error::Error for OsError {
     }
 }
 
+// If [`RawOsError`](https://doc.rust-lang.org/std/io/type.RawOsError.html) is stablized, we can use it.
+
+#[cfg(not(target_os = "uefi"))]
+type RawOsError = i32;
+
+#[cfg(target_os = "uefi")]
+type RawOsError = usize;
+
 impl OsError {
     /// Extract the raw OS error code (if this error came from the OS)
     ///
@@ -75,7 +83,7 @@ impl OsError {
     ///
     /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error
     #[inline]
-    pub fn raw_os_error(self) -> Option<i32> {
+    pub fn raw_os_error(self) -> Option<RawOsError> {
         self.0.raw_os_error()
     }
 }