Improved mac support

src/os/mac/Syscall.go

@@ -0,0 +1,10 @@
+package mac
+
+// Syscall numbers are divided into classes, here we need the BSD inherited syscalls.
+const SyscallClassUnix = 0x2000000
+
+// https://github.com/apple-oss-distributions/xnu/blob/main/bsd/kern/syscalls.master
+const (
+	Exit  = 1 | SyscallClassUnix
+	Write = 4 | SyscallClassUnix
+)