Use my-dir in a consistent way as others

Change-Id: I3fd0cc58b48d621b431d7dd05fb689c1917b530d
diff --git a/tools/Android.mk b/tools/Android.mk
index fa9d0b7..92603f5 100644
--- a/tools/Android.mk
+++ b/tools/Android.mk
@@ -14,7 +14,7 @@
 # limitations under the License.
 #
 
-LOCAL_PATH := $(my-dir)
+LOCAL_PATH := $(call my-dir)
 
 # If we're building only unbundled apps, this is the only tool we need.
 ifneq ($(TARGET_BUILD_APPS),)