Travis CI: Fix typo: The FORTRAN 77 impl build places its intermediates into the obj/ dir.
Travis CI: Fix typo: The FORTRAN 77 impl build places its intermediates into the obj/ dir.

rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang