Add comparekeys to release tarball

'make dist' omits lib/dns/tests/comparekeys/ (added in
7101afa23c) from release tarball it
creates which makes the unit:gcc:tarball CI job permanently fail in the
dst unit test.

lib/dns/tests/Makefile.am

@@ -109,6 +109,7 @@ rsa_test_CPPFLAGS =		\
 EXTRA_DIST =			\
 	Kdh.+002+18602.key	\
 	Krsa.+005+29235.key	\
+	comparekeys		\
 	mkraw.pl		\
 	testdata		\
 	testkeys