This means pkg-config couldn't find the guile-2.2.pc file associated with your Guile installation.
gEDA/gaf builds fine for me on Ubuntu 20.04. Did you install Guile to an unusual prefix?
You can test whether pkg-config is able to locate your Guile installation with pkg-config --print-errors guile-2.2 (no message means success).
This means pkg-config couldn't find the guile-2.2.pc file associated with your Guile installation.
gEDA/gaf builds fine for me on Ubuntu 20.04. Did you install Guile to an unusual prefix?
You can test whether pkg-config is able to locate your Guile installation with
pkg-config --print-errors guile-2.2
(no message means success).