Why not use the have function like before?
    
     auto/module
     64 if [ $NGX_DSO = YES ] ; then
     65     have=NGX_DSO . auto/have
     66     have=NGX_DSO_MAX value="$NGX_DSO_MAX" . auto/define
     67     have=NGX_DSO_PATH value="\"$NGX_DSO_PATH\"" . auto/define
     68     have=NGX_SOEXT value="\"$NGX_SOEXT\"" . auto/define