have the benchmarks import Darwin on macOS instead of Glibc

Author: tayloraswift

Tests/NoiseTests/main.swift

@@ -1,7 +1,12 @@
 import Noise
 import PNG
 
+// TODO: migrate the stdlib Clock APIs
+#if os(Linux)
 import func Glibc.clock
+#else 
+import func Darwin.clock 
+#endif
 
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