release-lib: add exception to build olm on hydra

Olm was marked as vulnerable in e4767b4.

The issue, however, is controversial and the practical ability to
exploit its vulnerabilities has not been demostrated: ultimately the
users are invited to decide for themselves.

Given that, hydra should still build and distribute the packages
depending on olm to avoid expensive builds in the event the users
decide it's acceptable to continue using these packages.

pkgs/top-level/release.nix

@@ -31,6 +31,11 @@
 , nixpkgsArgs ? { config = {
     allowUnfree = false;
     inHydra = true;
+    # Exceptional unsafe packages that we still build and distribute,
+    # so users choosing to allow don't have to rebuild them every time.
+    permittedInsecurePackages = [
+      "olm-3.2.16" # see PR #347899
+    ];
   }; }
 
   # This flag, if set to true, will inhibit the use of `mapTestOn`