add Int shim for Darwin.clock

Author: tayloraswift

Tests/NoiseTests/main.swift

@@ -6,6 +6,11 @@ import PNG
 import func Glibc.clock
 #else 
 import func Darwin.clock 
+
+func clock() -> Int 
+{
+    .init(Darwin.clock())
+}
 #endif
 
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