The new giggle was missing a few deps on my system: >=x11-libs/gtksourceview-3.0 >=x11-libs/vte-0.30
Sorry about that, I thought my dev scripts checked the configure.ac for version numbers, but apparently it didn't. I've now corrected the dependencies, thanks very much for informing me, do please let me know if there's any further issues... 5:)