Merge pull request #59365 from kateinoigakukun/katei/fix-single-threaded-build

[stubs] include unistd.h to repair swift-threading-package=none build

Author: al45tair

stdlib/public/stubs/Random.cpp

@@ -39,6 +39,10 @@
 
 #endif
 
+#if __has_include(<unistd.h>)
+#include <unistd.h>
+#endif
+
 #include <stdlib.h>
 
 #include "SwiftShims/Random.h"