python,python3: Disable user site-packages for host Python
Normally, Python will include the user's site-packages directory
(~/.local/lib/python$(PYTHON_VERSION)/site-packages) in it's internal
search path for modules.
This disables this default inclusion for host Python.
This change is applied during Host/Configure instead of as a patch to
keep this setting unchanged for target Python.
Signed-off-by: Jeffery To <jeffery.to@gmail.com>