WORKSPACE: bump bazel to 6.4.0

Change-Id: Id6ca8317c1eaeb55dc8f272fa51f8879c4c02320
Reviewed-on: https://review.monogon.dev/c/monogon/+/2261
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/third_party/nix/env.nix b/third_party/nix/env.nix
index c293036..2af72ff 100644
--- a/third_party/nix/env.nix
+++ b/third_party/nix/env.nix
@@ -40,8 +40,8 @@
     (stdenv.mkDerivation {
       name = "bazel";
       src = builtins.fetchurl {
-        url = https://github.com/bazelbuild/bazel/releases/download/5.4.0/bazel-5.4.0-linux-x86_64;
-        sha256 = "1w58m1brwjfwsv48fmd66inry67m4vgb3bwvwmamhdv099v183jg";
+        url = "https://github.com/bazelbuild/bazel/releases/download/6.4.0/bazel-6.4.0-linux-x86_64";
+        sha256 = "11md3cm9pb1449c3i89xy474v1lmzng5vbw6nhbigqx6xxqg7r3r";
       };
       unpackPhase = ''
         true
@@ -81,7 +81,7 @@
     curl
     gcc
     binutils
-    openjdk11
+    openjdk21
     patch
     python3
     busybox