feat(rustsec-advisory-db): update to 2021-10-08 via nix-prefetch-git

This makes it much easier to update the db manually and also lays the
foundation for future automation bumping the advisory db.

Change-Id: I1244020c8bb1af43bf4e207c55f6420eb3f57bcf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3713
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: Profpatsch <mail@profpatsch.de>

third_party/rustsec-advisory-db/default.nix

@@ -1,9 +1,24 @@
+# RustSec's advisory db for crates
+#
+# Update using:
+#
+#   nix-prefetch-git --quiet --url https://github.com/RustSec/advisory-db.git > third_party/rustsec-advisory-db/pin.json
+#
+# TODO(Profpatsch): automatically update in regular intervals
 { pkgs, ... }:
 
+let
+  pin = builtins.fromJSON (builtins.readFile ./pin.json);
+
+  date = builtins.head (builtins.split "T" pin.date);
+in
+
 pkgs.fetchFromGitHub {
+  name = "advisory-db-${date}";
   owner = "RustSec";
   repo = "advisory-db";
-  # TODO(Profpatsch): this will have to be updated regularly, how?
-  rev = "113188c62380753f01ff0df5edb7d67a300b143a";
-  sha256 = "0v086ybwr71zgs5nv8yr4w2w2d4daxx6in2s1sjb4m41q1r9p0wj";
+  inherit (pin)
+    rev
+    sha256
+  ;
 }