51b43e1ff0726d0c2fa088c075721a2fe4e1c7a1 build system bug fix

================================ DYNARE MAKE CHECK MATLAB RESULTS ================================ | TOTAL: 200 | PASS: 199 | FAIL: 0 | XFAIL: 1 | XPASS: 0

================================ DYNARE MAKE CHECK OCTAVE RESULTS ================================ | TOTAL: 198 | PASS: 197 | FAIL: 0 | XFAIL: 1 | XPASS: 0

A full log can be found on karaba in '/tmp/dynare-master-check-IC9UBl3fcN.log'.