Hi!

I have few questions again:

• Is there any idea supporting shared library?
  I found add_library(behavior_tree_core STATIC ${BT_Source} ). The library is forced to be static ever.

• Could fPIC be more relaxed?
  I found target_compile_options(behavior_tree_core PRIVATE "-fPIC"). However cmake provides POSITION_INDEPENDENT_CODE which is possible to be used as fPIC but as optional.

• Is there any idea supporting install target?
  I didn't find intall section in your cmake file. It could help all customers.

• Do you want export BehaviorTree using cmake config file?
  CMake provides helpers to exports all paths and libraries names in a single file.

• Is BehaviorTree supported on Windows and Macos?
  I found set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -pthread -Werror=return-type -Wall -Wpedantic -Wattributes") that is related to Linux (clang, gcc)

As I have some experience with CMake, I would be happy helping this project updating your cmake as well. I could create a separated PR introducing all changes.