[WIP] bazel: Add LLVM toolchain

.bazelrc

@@ -45,6 +45,13 @@ build:windows --action_env=PATH --host_action_env=PATH
 # Requires setting `BAZEL_VOLATILE_DIRTY` in the env.
 build --action_env=BAZEL_VOLATILE_DIRTY --host_action_env=BAZEL_VOLATILE_DIRTY
 
+# Prevent stamped caches from busting (eg in PRs)
+# Requires setting `BAZEL_FAKE_SCM_REVISION` in the env.
+build --action_env=BAZEL_FAKE_SCM_REVISION --host_action_env=BAZEL_FAKE_SCM_REVISION
+
+# build --incompatible_enable_cc_toolchain_resolution
+
+# build --enable_platform_specific_config
 build --test_summary=terse
 
 build:docs-ci --action_env=DOCS_RST_CHECK=1 --host_action_env=DOCS_RST_CHECK=1

WORKSPACE

@@ -31,3 +31,7 @@ envoy_dependency_imports()
 load("//bazel:dependency_imports_extra.bzl", "envoy_dependency_imports_extra")
 
 envoy_dependency_imports_extra()
+
+load("@llvm_toolchain//:toolchains.bzl", "llvm_register_toolchains")
+
+llvm_register_toolchains()

bazel/dependency_imports.bzl

@@ -18,6 +18,7 @@ load("@rules_rust//crate_universe:defs.bzl", "crates_repository")
 load("@rules_rust//crate_universe:repositories.bzl", "crate_universe_dependencies")
 load("@rules_rust//rust:defs.bzl", "rust_common")
 load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains", "rust_repository_set")
+load("@toolchains_llvm//toolchain:rules.bzl", "llvm_toolchain")
 
 # go version for rules_go
 GO_VERSION = "1.23.1"
@@ -175,6 +176,11 @@ def envoy_dependency_imports(go_version = GO_VERSION, jq_version = JQ_VERSION, y
     protoc_gen_jsonschema_go_dependencies()
     rules_proto_grpc_toolchains()
 
+    llvm_toolchain(
+        name = "llvm_toolchain",
+        llvm_version = "14.0.0",
+    )
+
 def envoy_download_go_sdks(go_version):
     go_download_sdk(
         name = "go_linux_amd64",

bazel/repositories.bzl

@@ -220,6 +220,7 @@ def envoy_dependencies(skip_targets = []):
     external_http_archive("bazel_toolchains")
     external_http_archive("bazel_compdb")
     external_http_archive("envoy_examples")
+    external_http_archive("toolchains_llvm")
 
     _com_github_maxmind_libmaxminddb()
 

bazel/repositories_extra.bzl

@@ -4,6 +4,7 @@ load("@com_google_protobuf//bazel/private:proto_bazel_features.bzl", "proto_baze
 load("@emsdk//:deps.bzl", emsdk_deps = "deps")
 load("@proxy_wasm_cpp_host//bazel/cargo/wasmtime/remote:crates.bzl", "crate_repositories")
 load("@rules_python//python:repositories.bzl", "py_repositories", "python_register_toolchains")
+load("@toolchains_llvm//toolchain:deps.bzl", "bazel_toolchain_dependencies")
 load("//bazel/external/cargo:crates.bzl", "raze_fetch_remote_crates")
 
 def _python_minor_version(python_version):
@@ -34,3 +35,5 @@ def envoy_dependencies_extra(
 
     if not native.existing_rule("proto_bazel_features"):
         proto_bazel_features(name = "proto_bazel_features")
+
+    bazel_toolchain_dependencies()

bazel/repository_locations.bzl

@@ -1536,6 +1536,19 @@ REPOSITORY_LOCATIONS_SPEC = dict(
         license = "Apache-2.0",
         license_url = "https://github.com/bazelbuild/rules_license/blob/{version}/LICENSE",
     ),
+    toolchains_llvm = dict(
+        project_name = "toolchains_llvm",
+        project_desc = "A LLVM toolchain for bazel",
+        project_url = "https://github.com/bazel-contrib/toolchains_llvm",
+        strip_prefix = "toolchains_llvm-v{version}",
+        version = "1.2.0",
+        sha256 = "e3fb6dc6b77eaf167cb2b0c410df95d09127cbe20547e5a329c771808a816ab4",
+        urls = ["https://github.com/bazel-contrib/toolchains_llvm/releases/download/v{version}/toolchains_llvm-v{version}.tar.gz"],
+        use_category = [],
+        extensions = [],
+        release_date = "2023-01-06",
+        cpe = "N/A",
+    ),
     utf8_range = dict(
         project_name = "utf8_range",
         project_desc = "Fast UTF-8 validation with Range algorithm (NEON+SSE4+AVX2)",