[Build] Use --warning=no-portability for autoreconf
[Build] Use --warning=no-portability for autoreconf

Assuming GNU Make in Automake is a quite safe thing to do given its
availability and enables us to write shorter/simpler rules.

Signed-off-by: Emanuele Aina <1df0c651b56ad56a4e0df13a7495e09f2634136f@collabora.com>

jku/dleyna-renderer,andhe/dleyna-renderer,UIKit0/dleyna-renderer,em-/dleyna-renderer,andhe/dleyna-renderer,01org/dleyna-renderer,rmerlino/dleyna-renderer,lferrandis/dleyna-renderer,UIKit0/dleyna-renderer,em-/dleyna-renderer,jku/dleyna-renderer,lferrandis/pkg-dleyna-renderer-debian,KobaltRo/dleyna-renderer,andhe/dleyna-renderer,debarshiray/dleyna-renderer,KobaltRo/dleyna-renderer,debarshiray/dleyna-renderer,debarshiray/dleyna-renderer,jku/dleyna-renderer,puleglot/dleyna-renderer,rmerlino/dleyna-renderer,lferrandis/dleyna-renderer,01org/dleyna-renderer,em-/dleyna-renderer,01org/dleyna-renderer,andhe/dleyna-renderer,puleglot/dleyna-renderer,debarshiray/dleyna-renderer,lferrandis/pkg-dleyna-renderer-debian,01org/dleyna-renderer,lferrandis/pkg-dleyna-renderer-debian,lferrandis/dleyna-renderer,em-/dleyna-renderer,KobaltRo/dleyna-renderer,lferrandis/dleyna-renderer,puleglot/dleyna-renderer,UIKit0/dleyna-renderer,rmerlino/dleyna-renderer,rmerlino/dleyna-renderer