Fix fail to build when building with introspection: in debian/ubuntu, builddir != srcdir. This trigger an error on introspection_files where srcdir is added to x11/*.c. Indeed, srcdir is added again later: $(addprefix $(srcdir)/,$(introspection_files)) making $(srcdir)/$(srcdir)/x11/*.c (not an issue on jhbuild as srcdir = .)
Fix fail to build when building with introspection:
in debian/ubuntu, builddir != srcdir. This trigger an error
on introspection_files where srcdir is added to x11/*.c.
Indeed, srcdir is added again later:
$(addprefix $(srcdir)/,$(introspection_files))
making $(srcdir)/$(srcdir)/x11/*.c (not an issue on jhbuild as srcdir = .)

Lyude/gtk-,davidgumberg/gtk,Adamovskiy/gtk,Distrotech/gtk2,msteinert/gtk,davidt/gtk,jessevdk/gtk,Lyude/gtk-,jadahl/gtk,chergert/gtk,jadahl/gtk,simokivimaki/gtk,ahodesuka/gtk,jadahl/gtk,davidgumberg/gtk,davidt/gtk,grubersjoe/adwaita,davidgumberg/gtk,alexlarsson/gtk,ahodesuka/gtk,msteinert/gtk,jadahl/gtk,simokivimaki/gtk,Adamovskiy/gtk,Sidnioulz/SandboxGtk,simokivimaki/gtk,Sidnioulz/SandboxGtk,ebassi/gtk,jigpu/gtk,simokivimaki/gtk,alexlarsson/gtk,msteinert/gtk,davidgumberg/gtk,ahodesuka/gtk,ahodesuka/gtk,davidt/gtk,grubersjoe/adwaita,simokivimaki/gtk,jessevdk/gtk,Lyude/gtk-,bratsche/gtk-,Sidnioulz/SandboxGtk,bratsche/gtk-,Adamovskiy/gtk,grubersjoe/adwaita,Distrotech/gtk2,alexlarsson/gtk,Lyude/gtk-,Adamovskiy/gtk,Distrotech/gtk2,chergert/gtk,Distrotech/gtk2,Sidnioulz/SandboxGtk,Adamovskiy/gtk,jadahl/gtk,jessevdk/gtk,jigpu/gtk,Adamovskiy/gtk,jigpu/gtk,alexlarsson/gtk,Distrotech/gtk2,ebassi/gtk,jadahl/gtk,grubersjoe/adwaita,jessevdk/gtk,ebassi/gtk,msteinert/gtk,simokivimaki/gtk,Distrotech/gtk2,ebassi/gtk,Lyude/gtk-,chergert/gtk,bratsche/gtk-,jadahl/gtk,chergert/gtk,jessevdk/gtk,alexlarsson/gtk,ahodesuka/gtk,davidgumberg/gtk,Adamovskiy/gtk,grubersjoe/adwaita,alexlarsson/gtk,grubersjoe/adwaita,jadahl/gtk,alexlarsson/gtk,bratsche/gtk-,msteinert/gtk,ebassi/gtk,Sidnioulz/SandboxGtk,jigpu/gtk,chergert/gtk,chergert/gtk,Lyude/gtk-,msteinert/gtk,Lyude/gtk-,grubersjoe/adwaita,ahodesuka/gtk,davidt/gtk,ahodesuka/gtk,alexlarsson/gtk,Lyude/gtk-,davidt/gtk,davidgumberg/gtk,bratsche/gtk-,chergert/gtk,jigpu/gtk,jessevdk/gtk,chergert/gtk,davidgumberg/gtk,jessevdk/gtk,bratsche/gtk-,grubersjoe/adwaita,Adamovskiy/gtk,jigpu/gtk,davidt/gtk,davidgumberg/gtk,ahodesuka/gtk,jigpu/gtk,ebassi/gtk,jigpu/gtk,Sidnioulz/SandboxGtk