[#3614737]Fix automake-1.14 run: add 'subdir-objects' into parameters.

Have subdirectories without 'subdir-objects' makes a warning in automake-1.14
which will bring a failure since we set '-Werror' for automake as well.
[#3614737]Add -Wno-portability for automake flags

The gtk-doc.make generates a fatal warning with automake-1.14.