Disable building NormalizInterface.

While that's not nice, it still seems better than disabling
digraphs, float and semigroups, which are far more complex packages,
and hence more likely to be broken by changes on master.

etc/ci.sh

@@ -50,9 +50,17 @@ do
 
     # skip linboxing because it hasn't compiled for years
     rm -rf linboxing*
+
     # skip PolymakeInterface: no polynmake installed (TODO: is there a polymake package we can use)
     rm -rf PolymakeInterface*
 
+    # skip NormalizInterface: currently fails to build due to lack of C++
+    # support in the install GMP (this only seems to appear when using GCC >= 5,
+    # so may be due to C++ ABI differences). Once we require C++ support in GAP,
+    # we can presumably re-enable it, if we switch the testpackge builds to use
+    # GAP's builtin GMP.
+    rm -rf NormalizInterface*
+
     # HACK to work out timestamp issues with anupq
     touch anupq*/configure* anupq*/Makefile* anupq*/aclocal.m4