After quite a lot of tweaking I was able to get to phase 2 of the building process with the code and notes from Waldek's GitHub repo.  Still having problems, mostly because I am using GCC 6.3.0 to build the older GCC and GPC source files.  There are some other issues with the older GCC's .info files that I corrected.

I just downloaded your gpc-3.4 .deb file.  You say to use gdebi, should apt or dpkg work also?  My Linux machine is headless.

-Ken