Add Publish to BCR setup (#363)

Author: fmeum

.bcr/metadata.template.json

@@ -0,0 +1,23 @@
+{
+  "homepage": "https://github.com/bazel-contrib/toolchains_llvm",
+  "maintainers": [
+    {
+      "email": "fabian@meumertzhe.im",
+      "github": "fmeum",
+      "name": "Fabian Meumertzheim"
+    },
+    {
+      "email": "james.sharpe@zenotech.com",
+      "github": "jsharpe",
+      "name": "James Sharpe"
+    },
+    {
+      "email": "rrbutani@users.noreply.github.com",
+      "github": "rrbutani",
+      "name": "Rahul Butani"
+    }
+  ],
+  "repository": ["github:bazel-contrib/toolchains_llvm"],
+  "versions": [],
+  "yanked_versions": {}
+}

.bcr/presubmit.yml

@@ -0,0 +1,25 @@
+matrix:
+  bazel: [7.x]
+  platform: [ubuntu2004, macos, macos_arm64]
+tasks:
+  verify_targets:
+    name: Verify build targets
+    bazel: ${{ bazel }}
+    platform: ${{ platform }}
+    build_targets:
+      - "@toolchains_llvm//toolchain:all"
+      - "@toolchains_llvm//platforms:all"
+bcr_test_module:
+  module_path: tests
+  matrix:
+    bazel: [7.x]
+    platform: [ubuntu2004, macos, macos_arm64]
+  tasks:
+    run_test_module:
+      name: Run test module
+      bazel: ${{ bazel }}
+      platform: ${{ platform }}
+      build_targets:
+        - //:all
+      test_targets:
+        - //:all

.bcr/source.template.json

@@ -0,0 +1,5 @@
+{
+  "integrity": "**leave this alone**",
+  "strip_prefix": "{REPO}-{VERSION}",
+  "url": "https://github.com/{OWNER}/{REPO}/releases/download/{TAG}/toolchains_llvm-{TAG}.tar.gz"
+}