Add kTruncate in FileBase. BUG=6841435.

And remove O_TRUNC from the default flags to OutputFile.

Change-Id: Id2ff6d5bac319d8be498e438eb3ef84e85573218
diff --git a/lib/RenderScript/RSExecutable.cpp b/lib/RenderScript/RSExecutable.cpp
index bbb31db..e18167a 100644
--- a/lib/RenderScript/RSExecutable.cpp
+++ b/lib/RenderScript/RSExecutable.cpp
@@ -128,7 +128,7 @@
   }
 
   android::String8 info_path = RSInfo::GetPath(*mObjFile);
-  OutputFile info_file(info_path.string());
+  OutputFile info_file(info_path.string(), FileBase::kTruncate);
 
   if (info_file.hasError()) {
     ALOGE("Failed to open the info file %s for write! (%s)", info_path.string(),