CMake can not find PythonLibs while building OpenCV

edit

so Im trying to cross-compile OpenCV for an arm device and while running cmake, I noticed in the output that the PythonLibs were not found. I have both Python2 and Python3 libs installed in my system.

Here is the output

-- Found PythonInterp: /usr/bin/python2.7 (found suitable version "2.7.12", minimum required is "2.7") -- Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS) (Required is exact version "2.7.12")

-- Found PythonInterp: /usr/bin/python3 (found suitable version "3.5.2", minimum required is "3.4") -- Could NOT find PythonLibs (missing: PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS) (Required is exact version "3.5.2")

Towards the end of the output, I also noticed this

Python 2: Interpreter: /usr/bin/python2.7 (ver 2.7.12)

Python 3: Interpreter: /usr/bin/python3 (ver 3.5.2)

Python (for build): /usr/bin/python2.7

From this I could conclude that the Python bindings were not built. If someone had any suggestion on how I can fix this, I would be happy to listen.