Attempt to fix OpenMP-related Travis CI failure

Error message is...

examples/blockedmm.c: In function ‘main’:
examples/blockedmm.c:90:52: error: ‘N’ is predetermined ‘shared’ for ‘firstprivate’
examples/blockedmm.c:90:52: error: ‘log2N’ is predetermined ‘shared’ for ‘firstprivate’
examples/blockedmm.c:90:52: error: ‘niter’ is predetermined ‘shared’ for ‘firstprivate’