BaseTools/GenSec: Fix potential memory leak

Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

BaseTools/Source/C/GenSec/GenSec.c

@@ -1670,7 +1670,11 @@ Finish:
   if (OutFile != NULL) {
     fclose (OutFile);
   }
-  
+
+  if (DummyFileBuffer != NULL) {
+    free (DummyFileBuffer);
+  }
+
   VerboseMsg ("%s tool done with return code is 0x%x.", UTILITY_NAME, GetUtilityStatus ());
 
   return GetUtilityStatus ();