Use pragma once over #define guards

Test: m
Change-Id: I3d0a1ef87618a963f0641733b5c7ebf849cb260a
diff --git a/include/nativehelper/toStringArray.h b/include/nativehelper/toStringArray.h
index df53b19..8d25974 100644
--- a/include/nativehelper/toStringArray.h
+++ b/include/nativehelper/toStringArray.h
@@ -14,8 +14,7 @@
  * limitations under the License.
  */
 
-#ifndef LIBNATIVEHELPER_INCLUDE_NATIVEHELPER_TOSTRINGARRAY_H_
-#define LIBNATIVEHELPER_INCLUDE_NATIVEHELPER_TOSTRINGARRAY_H_
+#pragma once
 
 #include "libnativehelper_api.h"
 
@@ -61,4 +60,3 @@
 
 #endif  // __cplusplus
 
-#endif  // LIBNATIVEHELPER_INCLUDE_NATIVEHELPER_TOSTRINGARRAY_H_