gtk3: Conversion from character set _UTF-8_ to _646_ is not supported

[Mayuresh <mayuresh%acm.org@localhost>]

When building x11/gtk3 in a recent pkgsrc on NetBSD 10.1 amd64 I get this:

FAILED: gdk/gdkresources.c 
/usr/pkg/bin/glib-compile-resources gdk/gdk.gresource.xml --sourcedir ../gdk --c-name _gdk --internal --generate --target gdk/gdkresources.c --manual-register --dependency-file gdk/gdkresources.c.d
GLib: Cannot convert message: Conversion from character set _UTF-8_ to _646_ is not supported
Conversion from character set _646_ to _UTF-8_ is not supported
[2/1581] Generating gdk/gdkresources_h with a custom command
FAILED: gdk/gdkresources.h 
/usr/pkg/bin/glib-compile-resources gdk/gdk.gresource.xml --sourcedir ../gdk --c-name _gdk --internal --generate --target gdk/gdkresources.h --manual-register
GLib: Cannot convert message: Conversion from character set _UTF-8_ to _646_ is not supported
Conversion from character set _646_ to _UTF-8_ is not supported
[4/1581] Generating GObject enum file gdk/gdkenumtypes.c (wrapped by meson to capture output)
ninja: build stopped: subcommand failed.

What could this be due to?

-- 
Mayuresh