build: Use --use-header for libvaladoc
build: Use --use-header for libvaladoc

Reduces the size of generated c-sources while avoiding redefinitions.

GNOME/vala,frida/vala,GNOME/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala,frida/vala,frida/vala