Fix a call to openat with incorrect arguments

Caught by running clang-FORTIFY over Android.

Bug: None
Test: Builds
Change-Id: If138c4bbb7f5fb40bbb20e24adbb25a6ef1286ac
(cherry picked from commit 7008c8484d2fa8761b8dcde3af1d62871a6c26d9)
diff --git a/debuggerd/tombstoned/tombstoned.cpp b/debuggerd/tombstoned/tombstoned.cpp
index 3c1dcaf..63e3dbd 100644
--- a/debuggerd/tombstoned/tombstoned.cpp
+++ b/debuggerd/tombstoned/tombstoned.cpp
@@ -110,7 +110,7 @@
   }
 
   result.reset(
-    openat(tombstone_directory_fd, buf, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, O_CLOEXEC, 0700));
+    openat(tombstone_directory_fd, buf, O_CREAT | O_EXCL | O_WRONLY | O_APPEND | O_CLOEXEC, 0700));
   if (result == -1) {
     PLOG(FATAL) << "failed to create tombstone at " << kTombstoneDirectory << buf;
   }