sys-apps/iucode_tool: Use unstable 2.3.1-r2 for a cross-compile fix

Signed-off-by: James Le Cuirot <jlecuirot@microsoft.com>

Author: chewi

sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.accept_keywords

@@ -124,3 +124,6 @@ sys-apps/azure-vm-utils
 # Our own ebuild fixing issues in Gentoo, hopefully will be fixed
 # there too eventually.
 =sys-libs/libselinux-3.8.1-r3 ~amd64 ~arm64
+
+# Needed to build this amd64-specific package on other arches.
+=sys-apps/iucode_tool-2.3.1-r2 ~amd64 ~arm64