[arch-general] Include paths for python 3

[Jayesh Badwaik]

I've noticed that the include paths for python 3 are updated according
to the version of python being installed. This removes some stability
for custom programs which build against python (example boost.python).
It would be nice if there was a symlink version of python include
paths to a stable location like `/usr/include/python3`.

Thank you.

-- 
Cheers
Jayesh Badwaik
https://jayeshbadwaik.gitlab.io