display: makefile fixes

* Deprecate LOCAL_COPY_HEADERS on newer builds
* Use a display header export path instead
* Consolidate cflags

CRs-Fixed: 2023356
Change-Id: Ibb8900a77fc3fa47e6e54cd1649503eba12de8cd
diff --git a/sdm/libs/hwc2/Android.mk b/sdm/libs/hwc2/Android.mk
index d4ff53c..aeb2558 100644
--- a/sdm/libs/hwc2/Android.mk
+++ b/sdm/libs/hwc2/Android.mk
@@ -8,6 +8,7 @@
 LOCAL_MODULE_RELATIVE_PATH    := hw
 LOCAL_MODULE_TAGS             := optional
 LOCAL_C_INCLUDES              := $(common_includes)
+LOCAL_HEADER_LIBRARIES        := display_headers
 
 LOCAL_CFLAGS                  := -Wno-missing-field-initializers -Wno-unused-parameter \
                                  -std=c++11 -fcolor-diagnostics\