processUNIX: close intermediate file descriptor in error case

ProcessUNIX.c

@@ -1938,6 +1938,7 @@ static int kwsysProcessSetupOutputPipeFile(int* p, const char* name)
 
   /* Set close-on-exec flag on the pipe's end.  */
   if (fcntl(fout, F_SETFD, FD_CLOEXEC) < 0) {
+    close(fout);
     return 0;
   }