Update libgsystem

Now with new shiny implementation of gs_shutil_rm_rf().

diff --git a/src/libgsystem b/src/libgsystem
index bd2c1e436b270b39ca262765e775b4556d6bd50b..7b9901e3fc8aa58cf9c0579c29340506269ebfbd 160000 (submodule)
--- a/src/libgsystem
+++ b/src/libgsystem
@@ -1 +1 @@
-Subproject commit bd2c1e436b270b39ca262765e775b4556d6bd50b
+Subproject commit 7b9901e3fc8aa58cf9c0579c29340506269ebfbd