libsensors: Fix build breakage. Don't build IIO hal unless requested

Avoid building the libinvensense_hal and other libs unless
IIO is requested.

Change-Id: I051c501bd3267e72cc4d66544dbbbbd5418ae680
diff --git a/libsensors/Android.mk b/libsensors/Android.mk
index f6c9323..2b704db 100644
--- a/libsensors/Android.mk
+++ b/libsensors/Android.mk
@@ -16,6 +16,7 @@
 LOCAL_PATH := $(call my-dir)
 
 ifneq ($(TARGET_SIMULATOR),true)
+ifeq ($(BUILD_INVENSENSE_IIO_HAL), true)
 
 # InvenSense fragment of the HAL
 include $(CLEAR_VARS)
@@ -141,4 +142,5 @@
 OVERRIDE_BUILT_MODULE_PATH := $(TARGET_OUT_INTERMEDIATE_LIBRARIES)
 include $(BUILD_PREBUILT)
 
+endif # BUILD_INVENSENSE_IIO_HAL
 endif # !TARGET_SIMULATOR