GtkD master builds fine for me using LDC built from master on both Debian Sid and Fedora Rawhide, and gdc 4.9 on Debian Sid and gdc 5.0 on Fedora Rawhide. However, using dmd 2.066 on both Debian Sid and Fedora Rawhide, the GtkD build fails. On Debian Sid (and also on Fedora Rawhide I believe, but I will need to check) I get:
dmd -O -m64 -Isrc -Idemos/gtkD/TestWindow -c demos/gtkD/TestWindow/TestStock.d -ofdemos/gtkD/TestWindow/TestStock.o
Internal error: backend/go.d 242
so it's not GtkD itself that's the problem, but this is terminating the build early and so inhibiting installation.