use target property to locate system-installed libbson include dir (#1084)

Author: rcsanchez97

cmake/ImportBSON.cmake

@@ -75,7 +75,9 @@ function (_import_bson)
       message (STATUS "NOTE: Using system-wide libbson library. This is intended only for package maintainers.")
       find_library (_MONGOCRYPT_SYSTEM_LIBBSON_SHARED "${CMAKE_SHARED_LIBRARY_PREFIX}bson2${CMAKE_SHARED_LIBRARY_SUFFIX}")
       find_library (_MONGOCRYPT_SYSTEM_LIBBSON_STATIC "${CMAKE_STATIC_LIBRARY_PREFIX}bson2${CMAKE_STATIC_LIBRARY_SUFFIX}")
-      find_path (_MONGOCRYPT_SYSTEM_LIBBSON_INCLUDE_DIR bson/bson.h PATH_SUFFIXES bson-2.1.0)
+      find_package (bson 2.0 REQUIRED)
+      get_target_property (_BSON_SHARED_INCL_DIR_PROP bson::shared INTERFACE_INCLUDE_DIRECTORIES)
+      set (_MONGOCRYPT_SYSTEM_LIBBSON_INCLUDE_DIR "${_BSON_SHARED_INCL_DIR_PROP}" CACHE FILEPATH "Internal use only")
       add_library (bson_shared SHARED IMPORTED)
       add_library (bson_static STATIC IMPORTED)
       set_target_properties (bson_shared bson_static PROPERTIES