fix clippy warnings

(backport <rust-lang#3855>)
[ drop change to `.split` that doesn't work with old rustc - Trevor ]
(cherry picked from commit a438a21)

build.rs

@@ -216,7 +216,6 @@ fn rustc_minor_nightly() -> (u32, bool) {
     let output = cmd
         .arg("--version")
         .output()
-        .ok()
         .expect("Failed to get rustc version");
     if !output.status.success() {
         panic!(

src/unix/bsd/apple/mod.rs

@@ -5564,19 +5564,19 @@ f! {
             return ::CMSG_FIRSTHDR(mhdr);
         };
         let cmsg_len = (*cmsg).cmsg_len as usize;
-        let next = cmsg as usize + __DARWIN_ALIGN32(cmsg_len as usize);
+        let next = cmsg as usize + __DARWIN_ALIGN32(cmsg_len);
         let max = (*mhdr).msg_control as usize
                     + (*mhdr).msg_controllen as usize;
         if next + __DARWIN_ALIGN32(::mem::size_of::<::cmsghdr>()) > max {
-            0 as *mut ::cmsghdr
+            core::ptr::null_mut()
         } else {
             next as *mut ::cmsghdr
         }
     }
 
     pub fn CMSG_DATA(cmsg: *const ::cmsghdr) -> *mut ::c_uchar {
         (cmsg as *mut ::c_uchar)
-            .offset(__DARWIN_ALIGN32(::mem::size_of::<::cmsghdr>()) as isize)
+            .add(__DARWIN_ALIGN32(::mem::size_of::<::cmsghdr>()))
     }
 
     pub {const} fn CMSG_SPACE(length: ::c_uint) -> ::c_uint {

src/unix/bsd/mod.rs

@@ -548,7 +548,7 @@ f! {
         if (*mhdr).msg_controllen as usize >= ::mem::size_of::<::cmsghdr>() {
             (*mhdr).msg_control as *mut ::cmsghdr
         } else {
-            0 as *mut ::cmsghdr
+            core::ptr::null_mut()
         }
     }