How to fix catkin_make error for px-ros-pkg?

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Hello,

I am trying to use the ROS interface for the PX4flow optical flow board. I git cloned px-ros-pkg into my catkin workspace src subdirectory. This is what i get when i catkin_make:-

 Base path: /home/aman/new_catkin_ws
Source space: /home/aman/new_catkin_ws/src
Build space: /home/aman/new_catkin_ws/build
Devel space: /home/aman/new_catkin_ws/devel
Install space: /home/aman/new_catkin_ws/install
####
#### Running command: "make cmake_check_build_system" in "/home/aman/new_catkin_ws/build"
####
-- Using CATKIN_DEVEL_PREFIX: /home/aman/new_catkin_ws/devel
-- Using CMAKE_PREFIX_PATH: /opt/ros/hydro
-- This workspace overlays: /opt/ros/hydro
-- Using Debian Python package layout
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/aman/new_catkin_ws/build/test_results
-- Found gtest sources under '/usr/src/gtest': gtests will be built
-- catkin 0.5.74
-- BUILD_SHARED_LIBS is on
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- ~~  traversing 3 packages in topological order:
-- ~~  - px_comm
-- ~~  - mavlink_serial_client
-- ~~  - px4flow
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- +++ processing catkin package: 'px_comm'
-- ==> add_subdirectory(px-ros-pkg/px_comm)
-- px_comm: 3 messages, 1 services
-- +++ processing catkin package: 'mavlink_serial_client'
-- ==> add_subdirectory(px-ros-pkg/drivers/mavlink_serial_client)
CMake Error at /home/aman/new_catkin_ws/devel/share/px_comm/cmake/px_commConfig.cmake:130 (message):
  Project 'mavlink_serial_client' tried to find library 'px_comm_dds'.  The
  library is neither a target nor built/installed properly.  Did you compile
  project 'px_comm'? Did you find_package() it before the subdirectory
  containing its code is included?
Call Stack (most recent call first):
  /opt/ros/hydro/share/catkin/cmake/catkinConfig.cmake:72 (find_package)
  px-ros-pkg/drivers/mavlink_serial_client/CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
make: *** [cmake_check_build_system] Error 1
Invoking "make cmake_check_build_system" failed

Why is this happening and what is the fix? Thanks.