verify-sig.eclass: Predict attempted writes to /run/user

Signed-off-by: Michał Górny <mgorny@gentoo.org>

eclass/verify-sig.eclass

@@ -98,6 +98,11 @@ verify-sig_verify_detached() {
 		--keyserver "${VERIFY_SIG_OPENPGP_KEYSERVER}"
 	)
 
+	# GPG upstream knows better than to follow the spec, so we can't
+	# override this directory.  However, there is a clean fallback
+	# to GNUPGHOME.
+	addpredict /run/user
+
 	einfo "Verifying ${file##*/} ..."
 	gemato gpg-wrap -K "${key}" "${extra_args[@]}" -- \
 		gpg --verify "${sig}" "${file}" ||