add an option to use prebuilts

Change-Id: I340fb240f4109cddfda70cd17a07d06fef0b8209
diff --git a/als/Android.mk b/als/Android.mk
index 7d756fc..9a1d5db 100644
--- a/als/Android.mk
+++ b/als/Android.mk
@@ -13,6 +13,8 @@
 # limitations under the License.
 #
 
+ifeq ($(USE_SENSOR_HAL_PREBUILTS),false)
+
 LOCAL_PATH := $(call my-dir)
 
 # HAL module implemenation, not prelinked, and stored in
@@ -84,3 +86,5 @@
 LOCAL_SHARED_LIBRARIES := liblog libutils libdl
 
 include $(BUILD_SHARED_LIBRARY)
+
+endif # USE_SENSOR_HAL_PREBUILTS
diff --git a/libsensors_iio/src/Android.mk b/libsensors_iio/src/Android.mk
index ca2d400..aa5f757 100644
--- a/libsensors_iio/src/Android.mk
+++ b/libsensors_iio/src/Android.mk
@@ -15,6 +15,8 @@
 # limitations under the License.
 #/
 
+ifeq ($(USE_SENSOR_HAL_PREBUILTS),false)
+
 ifneq ($(TARGET_SIMULATOR),true)
 
 LOCAL_PATH := $(call my-dir)
@@ -171,3 +173,5 @@
 include $(call all-makefiles-under, $(LOCAL_PATH))
 
 endif # !TARGET_SIMULATOR
+
+endif # USE_SENSOR_HAL_PREBUILTS
diff --git a/tilt/Android.mk b/tilt/Android.mk
index 3b543a3..6c5f9d5 100644
--- a/tilt/Android.mk
+++ b/tilt/Android.mk
@@ -13,6 +13,8 @@
 # limitations under the License.
 #
 
+ifeq ($(USE_SENSOR_HAL_PREBUILTS),false)
+
 LOCAL_PATH := $(call my-dir)
 
 # HAL module implemenation, not prelinked, and stored in
@@ -85,3 +87,4 @@
 
 include $(BUILD_SHARED_LIBRARY)
 
+endif # USE_SENSOR_HAL_PREBUILTS