Fix compiler determination on Mac OS X.
Fix compiler determination on Mac OS X.

neurodebian/htcondor,htcondor/htcondor,neurodebian/htcondor,neurodebian/htcondor,neurodebian/htcondor,neurodebian/htcondor,htcondor/htcondor,neurodebian/htcondor,htcondor/htcondor,htcondor/htcondor,neurodebian/htcondor,neurodebian/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,neurodebian/htcondor