Trouble with amcheck

I just cloned PostgreSQL to a new machine today (Ubuntu 17.04). "make
install" and "make check-world" run fine but "make installcheck-world" is
having trouble with amcheck:

In contrib/amcheck/results:

CREATE EXTENSION amcheck;
ERROR: could not open extension control file
"/home/doole/pgCommunity/install/share/postgresql/extension/amcheck.control":
No such file or directory

I expect I'm missing something in the machine set up, but I'm stumped as to
what.

Any suggestions?

Thanks

- Doug