How to configure Android.bp to include other project's whole source directory

[Eunryoung Lim]

Hello,

I have read followings

- How to include external header files in cc_binary build

- How to add relative path for srcs:[] in Android.bp

to see the usecase of filegroup in soong build system.
What if we want to include (copy) whole directory structure rather than a few source and header files?

For instance, in project1 source code will be generated based on the given idl (input_idl) files. Then, generated code will be utilized in other projects, which could be either library or binary.

As far as I understand, filegroup is not available to include whole directory. Is it correct? 
What would be the best solution for this? (I am considering creating a static library).

Any comments will be appreciated.

project1
 - input_idl    
 - src-gen
   - dir1
     - *.cpp
     - *.hpp

project2
  - src
  - src-gen (from project1, also it might need to be in export_include_dirs)

project3 
  - src
  - src-gen (from project1)

Best Regards,

Eunryoung