Silence Clippy incompatible_msrv (#122)

* Silence Clippy incompatible_msrv

This is due to rust-lang/libc#5015.

* Use `clippy::msrv` instead

* Formatting

Author: lambda-fairy

src/unix.rs

@@ -100,5 +100,10 @@ extern "C" {
     )]
     #[cfg_attr(target_os = "aix", link_name = "_Errno")]
     #[cfg_attr(target_os = "nto", link_name = "__get_errno_ptr")]
+    // Newer libc versions re-export `c_int` from `std` which is incompatible
+    // with Rust < 1.64. However, this is not actually a problem as users can
+    // use an older `libc`.
+    // See: https://github.com/rust-lang/libc/pull/5015
+    #[clippy::msrv = "1.64"]
     fn errno_location() -> *mut c_int;
 }