Allow google dialer code to be compiled against M and N SDKs

+ Defaulted src-N to source directory in makefile

Bug:26330692
Change-Id: I62b3644fb05ace592cf989781f059d214d6c42d9
diff --git a/Android.mk b/Android.mk
index b0fa901..ad13292 100644
--- a/Android.mk
+++ b/Android.mk
@@ -16,6 +16,8 @@
 res_dirs := res $(contacts_common_dir)/res $(phone_common_dir)/res
 asset_dirs := $(contacts_common_dir)/assets
 
+src_dirs += src-N $(contacts_common_dir)/src-N $(phone_common_dir)/src-N
+
 LOCAL_SRC_FILES := $(call all-java-files-under, $(src_dirs))
 LOCAL_RESOURCE_DIR := $(addprefix $(LOCAL_PATH)/, $(res_dirs)) \
     $(support_library_root_dir)/v7/appcompat/res \