Don't manually link libgtest_main in libion tests.

This is actually probably broken right now, since these tests are
getting both the libc++ flavor and stlport flavor of libgtest_main.

Bug: 15193147
Change-Id: Ic2f8dda98240c12591803f3c3522505314a05609
diff --git a/libion/tests/Android.mk b/libion/tests/Android.mk
index 8dc7f9d..abf527a 100644
--- a/libion/tests/Android.mk
+++ b/libion/tests/Android.mk
@@ -21,7 +21,6 @@
 LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
 LOCAL_CFLAGS += -g -Wall -Werror -std=gnu++11 -Wno-missing-field-initializers
 LOCAL_SHARED_LIBRARIES += libion
-LOCAL_STATIC_LIBRARIES += libgtest_main
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/../kernel-headers
 LOCAL_SRC_FILES := \
 	ion_test_fixture.cpp \