seems i have problems with the system ones, wich is is older version (https://aur.archlinux.org/packages/python-glad) but setting PYTHONPATH="${srcdir}/libplacebo/3rdparty/glad" or leaving unset after ...
LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 9) LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format ...