Add more minimal CI test

Author: terhorstd

.github/workflows/nestbuildmatrix.yml

@@ -524,6 +524,7 @@ jobs:
         # available use flags (all default to "OFF"):
         # openmp, mpi, python, gsl, ltdl, boost, sionlib, libneurosim, optimize, warning, userdoc, music
         use:
+          - "optimize, warning"
           - "boost, optimize, warning"
           - "openmp, python, gsl, ltdl, boost, optimize, warning"
           - "mpi, python, gsl, ltdl, boost, optimize, warning"