std.c: define MADV for darwin

Author: GabeRealB

lib/std/c.zig

@@ -1360,6 +1360,20 @@ pub const KERN = switch (native_os) {
 pub const MADV = switch (native_os) {
     .linux => linux.MADV,
     .emscripten => emscripten.MADV,
+    .macos, .ios, .tvos, .watchos, .visionos => struct {
+        pub const NORMAL = 0;
+        pub const RANDOM = 1;
+        pub const SEQUENTIAL = 2;
+        pub const WILLNEED = 3;
+        pub const DONTNEED = 4;
+        pub const FREE = 5;
+        pub const ZERO_WIRED_PAGES = 6;
+        pub const FREE_REUSABLE = 7;
+        pub const FREE_REUSE = 8;
+        pub const CAN_REUSE = 9;
+        pub const PAGEOUT = 10;
+        pub const ZERO = 11;
+    },
     .freebsd => struct {
         pub const NORMAL = 0;
         pub const RANDOM = 1;