make dvmOpenCachedDexFile resistant to umask changes.

Change-Id: I61734941bd94a013a82c1dd0ebeac43fefa680e1
diff --git a/vm/analysis/DexPrepare.c b/vm/analysis/DexPrepare.c
index 0f82cbf..fce09e2 100644
--- a/vm/analysis/DexPrepare.c
+++ b/vm/analysis/DexPrepare.c
@@ -104,6 +104,8 @@
             return fd;
         }
         readOnly = true;
+    } else {
+        fchmod(fd, 0644);
     }
 
     /*