Release v3.21.2 (#71)

* Prepare release v3.21.2

* Update the state.json for v3.21.2

* Update README.md and action.yml for v3.21.2

* flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.1011622%2Brev-a799d3e3886da994fa307f817a6bc705ae538eeb/019ea4be-9303-7001-8232-6b7ec45c4f5b/source.tar.gz' (2026-06-06)
  → 'https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.1.1017464%2Brev-567a49d1913ce81ac6e9582e3553dd90a955875f/019ed27e-44b2-7462-b1ef-3564aa6c28ee/source.tar.gz' (2026-06-16)

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

action.yml

@@ -72,12 +72,20 @@
         "source-tag": {
             "description": "The tag of `nix-installer` to use (conflicts with `source-revision`, `source-branch`, `source-pr`)",
             "required": false,
-            "default": "v3.21.1"
+            "default": "v3.21.2"
         },
         "source-url": {
             "description": "A URL pointing to a `nix-installer` executable",
             "required": false
         },
+        "source-checksums-url": {
+            "description": "URL of a `shasum`-format checksums file listing the SHA-256 of each\n`nix-installer-<arch>-<os>` artifact. Used together with\n`source-checksums-sha256` to verify the downloaded installer.\n",
+            "required": false
+        },
+        "source-checksums-sha256": {
+            "description": "Pinned SHA-256 (hex) of the file served at `source-checksums-url`. Must\nbe set together with `source-checksums-url`.\n",
+            "required": false
+        },
         "backtrace": {
             "description": "The setting for `RUST_BACKTRACE` (see https://doc.rust-lang.org/std/backtrace/index.html#environment-variables)",
             "required": false
@@ -105,7 +113,7 @@
         "using": "composite",
         "steps": [
             {
-                "uses": "DeterminateSystems/nix-installer-action@1d87d45818068401a10cf16bdc5f00b24994a83f",
+                "uses": "DeterminateSystems/nix-installer-action@a7ad9c4f0c65208097f4d34f3cfa1913b80cce5c",
                 "with": {
                     "extra-conf": "${{ inputs.extra-conf }}",
                     "github-server-url": "${{ inputs.github-server-url }}",
@@ -124,6 +132,8 @@
                     "source-revision": "${{ inputs.source-revision }}",
                     "source-tag": "${{ inputs.source-tag }}",
                     "source-url": "${{ inputs.source-url }}",
+                    "source-checksums-url": "${{ inputs.source-checksums-url }}",
+                    "source-checksums-sha256": "${{ inputs.source-checksums-sha256 }}",
                     "backtrace": "${{ inputs.backtrace }}",
                     "diagnostic-endpoint": "${{ inputs.diagnostic-endpoint }}",
                     "log-directives": "${{ inputs.log-directives }}",