use Security.framework with SecRandomCopyBytes for rand_bytes on darwin

core/sys/darwin/security.odin

@@ -0,0 +1,24 @@
+//+build darwin
+package darwin
+
+foreign import security "system:Security.framework"
+
+// A reference to a random number generator.
+SecRandomRef :: distinct rawptr
+
+OSStatus :: distinct i32
+
+errSec :: enum OSStatus {
+	Success       = 0,  // No error.
+	Unimplemented = -4, // Function or operation not implemented.
+
+	// Many more...
+}
+
+foreign security {
+	// Synonym for nil, uses a cryptographically secure random number generator.
+	kSecRandomDefault: SecRandomRef
+	
+	// Generates an array of cryptographically secure random bytes.
+	SecRandomCopyBytes :: proc(rnd: SecRandomRef = kSecRandomDefault, count: uint, bytes: [^]byte) -> errSec ---
+}