travis: fix autotools build after --enable-autotools switch addition

Fixes: e68777c87c "autotools: Deprecate the use of autotools"
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Acked-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

.travis.yml

@@ -805,7 +805,9 @@ script:
 
       mkdir build &&
       cd build &&
-      ../autogen.sh --enable-debug
+      ../autogen.sh
+        --enable-autotools
+        --enable-debug
         $LIBUNWIND_FLAGS
         $DRI_LOADERS
         --with-dri-drivers=$DRI_DRIVERS