Please write CMake scripts in a modern style, and follow the best practices in Effective Modern CMake.
Use the bolt_add_library command to add CMake target. It is a wrapper of the add_library command(see here.
It will turn this target into an OBJECT target, and categorize and assemble it into the correct Bolt's sub-components.
Take this CMake target bolt_config for example:
# Step 1: turn bolt_config into an OBJECT target.
# Step 2: add bolt_config into bolt_engine sub-component according to its directory hierarchy.
bolt_add_library(bolt_config Config.cpp Context.cpp)
target_link_libraries(bolt_config PUBLIC Folly::folly)