Allow properties to be overriden by arch variants.
Add include_dirs and local_include_dirs properties.
Pass -I . to fix:
frameworks/base/proto/src/metrics_constants.proto: File does not
reside within any path specified using --proto_path (or -I). You
must specify a --proto_path which encompasses this file. Note that
the proto_path must be an exact prefix of the .proto file names --
protoc is too dumb to figure out when two paths (e.g. absolute and
relative) are equivalent (it's harder than you think).
Test: m -j libplatformprotos
Change-Id: I3e02621ca25bfa7ca0a0e3b83377d70dd352668f