add returned include dir as --proto_path

[justai-net]

Attempt to fix other issues around #8

protoc --decode google.protobuf.FileDescriptorSet /usr/local/include/google/protobuf/descriptor.proto
/usr/local/include/google/protobuf/descriptor.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).

Will now perform

protoc -I /path/to --decode google.protobuf.FileDescriptorSet /path/to/google/protobuf/descriptor.proto

Signed-off-by: Adam Inthapanya adam.int@live.com

[rohanray]

@justai-net @stevvooe This PR works for me.

[stevvooe]

LGTM