ROS 2 Software, unable to build from source

[MelodicMagnesium]

following instructions to build from source in ros2 foxy.

git clone --branch master https://github.com/RoverRobotics-forks/serial-ros2.git
git clone --branch ros2 https://github.com/ros-drivers/um7.git 

next when I execute this
colcon build --packages-select serial umx_driver

give this error

Starting >>> serial  
Finished <<< serial [2.89s]                     
Starting >>> umx_driver
--- stderr: umx_driver                         
CMake Error at CMakeLists.txt:68 (rosidl_get_typesupport_target):
  Unknown CMake command "rosidl_get_typesupport_target".


---
Failed   <<< umx_driver [3.98s, exited with code 1]

Summary: 1 package finished [7.53s]
  1 package failed: umx_driver
  1 package had stderr output: umx_driver

When I try building from source on a different distro (humble), it compiles without any issue and the example works flawlessly.