build: update gnulib for Solaris 10 unsetenv work-around

diff --git a/gnulib b/gnulib
index eedd7fff3193f2e0b81841d873fbf199358f7e68..3e00f5fce5b904dc642aff88abbcf75867263e0a 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit eedd7fff3193f2e0b81841d873fbf199358f7e68
+Subproject commit 3e00f5fce5b904dc642aff88abbcf75867263e0a