Add libselinux to the Rust allowlist so we can run its test.

Test: Build and atest
Change-Id: Id828f286b35decfd16166e9cbb78cdf477014bf6
diff --git a/rust/config/allowed_list.go b/rust/config/allowed_list.go
index e527aea..926d2ac 100644
--- a/rust/config/allowed_list.go
+++ b/rust/config/allowed_list.go
@@ -12,6 +12,7 @@
 		"external/libchromeos-rs",
 		"external/minijail",
 		"external/rust",
+		"external/selinux/libselinux",
 		"external/vm_tools/p9",
 		"frameworks/native/libs/binder/rust",
 		"frameworks/proto_logging/stats",