Bug#975878: libyade is still linked with libpython3.8

[Adrian Bunk]

Source: yade
Version: 2020.01a-12
Severity: serious

libyade is still linked with libpython3.8 after the
rebuild with 3.9 as default, likely due to
https://sources.debian.org/src/yade/2020.01a-12/CMakeLists.txt/#L196