The CMakeLists.txt configuration for the C driver build currently specifies some compile definitions and include directories at the directory level. This was likely done so that the properties would apply to every target in a given directory (e.g., every variant of libbson and every variant of libmongoc). However, this prevents correctly referencing the targets from an external project that includes the C driver as a sub-project in a sub-directory of the parent project build. In order to correct this it is necessary to migrate the specification of compile definitions and include directories to attach them directly to targets in every case.