Fix multiple inclusion guards to match new pathnames

Change-Id: Id7735be1d75bc315733b1773fba45c1deb8ace43
diff --git a/runtime/base/unix_file/null_file.h b/runtime/base/unix_file/null_file.h
index e716603..3394731 100644
--- a/runtime/base/unix_file/null_file.h
+++ b/runtime/base/unix_file/null_file.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef BASE_UNIX_FILE_NULL_FILE_H_
-#define BASE_UNIX_FILE_NULL_FILE_H_
+#ifndef ART_RUNTIME_BASE_UNIX_FILE_NULL_FILE_H_
+#define ART_RUNTIME_BASE_UNIX_FILE_NULL_FILE_H_
 
 #include "base/unix_file/random_access_file.h"
 #include "base/macros.h"
@@ -47,4 +47,4 @@
 
 }  // namespace unix_file
 
-#endif  // BASE_UNIX_FILE_NULL_FILE_H_
+#endif  // ART_RUNTIME_BASE_UNIX_FILE_NULL_FILE_H_