Add missing headers to libbt-vendor

When building with BOARD_VNDK_VERSION set, global include path is not
provided. As a result, libbt-vendor could not be built since it has been
using some symbols without explicitly including headers.

This CL adds the missing headers and organize the include path order.

Bug: 37342627
Test: BOARD_VNDK_VERSION=current m -j libbt-vendor
Change-Id: Icc16cef0aa6bd8911fb2a36bc4016e1f5b110471
diff --git a/libbt-vendor/Android.mk b/libbt-vendor/Android.mk
index cb66f5a..be69144 100644
--- a/libbt-vendor/Android.mk
+++ b/libbt-vendor/Android.mk
@@ -65,6 +65,9 @@
         libcutils \
         liblog
 
+LOCAL_HEADER_LIBRARIES := \
+        libutils_headers
+
 LOCAL_MODULE := libbt-vendor
 LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE_CLASS := SHARED_LIBRARIES