scrypt: Don't hardcode gtest path.

Bug: http://b/16574165
Change-Id: Ieb63fb6a73f0fb2ab3260bc5eabca7d86d892fbd
diff --git a/crypto/scrypt/tests/Android.mk b/crypto/scrypt/tests/Android.mk
index c20b41d..b49d8a1 100644
--- a/crypto/scrypt/tests/Android.mk
+++ b/crypto/scrypt/tests/Android.mk
@@ -8,9 +8,7 @@
 LOCAL_SRC_FILES:= \
     scrypt_test.cpp
 
-LOCAL_C_INCLUDES := \
-    external/gtest/include \
-    external/scrypt/lib/crypto
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/../lib/crypto
 
 LOCAL_SHARED_LIBRARIES := \
     libcrypto