Hey Alan!

 AI> In both cases there is a fatal error early in the build of
 AI> cryptlib because it fails to find cryptlib.

find shows it located in ./3rdp/src/cl/cryptlib.h.

 AI> It says no such file or directory. I wonder why it's failing
 AI> here?

Not sure but it might be something to do with your path.  See COMPILNG in the syncterm directory of the source.  It mentions setting up SRC_ROOT in the commandline.  I didn't have to do that here and simply switched to the directory ./syncterm-20230302/src/syncterm/ and run make.  Also I haven't bothered installing it anywhere.

Life is good,
Maurice

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