Add CPU_ALLOC_SIZE

Co-Authored-By: Yuki Okushi <huyuumi.dev@gmail.com>

src/unix/linux_like/linux/mod.rs

@@ -2620,6 +2620,12 @@ f! {
         }
     }
 
+    pub fn CPU_ALLOC_SIZE(count: ::c_int) -> ::size_t {
+        let _dummy: cpu_set_t = ::mem::zeroed();
+        let size_in_bits = 8 * ::mem::size_of_val(&_dummy.bits[0]);
+        ((count as ::size_t + size_in_bits - 1) / 8) as ::size_t
+    }
+
     pub fn CPU_ZERO(cpuset: &mut cpu_set_t) -> () {
         for slot in cpuset.bits.iter_mut() {
             *slot = 0;