documentation-builder: Use C.UTF-8 locale
Python and locales is pretty horrible. When using the default C locale, it will try to interpret some things as ascii rather then unicode/utf-8. Which can blow up when doing e.g. pip3 install. Switch to C.UTF-8 instead which is is an UTF-8 using variant of C
Signed-off-by: Sjoerd Simons sjoerd.simons@collabora.co.uk