build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 0b06bc0c0f0617ee6a1be9b67944e34bedb23f63..e54b645fc6b8422562327443bda575c65d931fbd 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 0b06bc0c0f0617ee6a1be9b67944e34bedb23f63
+Subproject commit e54b645fc6b8422562327443bda575c65d931fbd