set up llvm

MODULE.bazel

@@ -23,6 +23,19 @@ register_toolchains(
     "@rules_foreign_cc//toolchains:preinstalled_make_toolchain",
 )
 
+
+bazel_dep(name = "toolchains_llvm", version = "1.2.0")
+
+# Configure and register the toolchain.
+llvm = use_extension("@toolchains_llvm//toolchain/extensions:llvm.bzl", "llvm")
+llvm.toolchain(
+   llvm_version = "18.1.8",
+)
+
+use_repo(llvm, "llvm_toolchain")
+
+register_toolchains("@llvm_toolchain//:all")
+
 # Use HEAD to include this commit which is needed for preinstalled toolchains to work
 # https://github.com/bazel-contrib/rules_foreign_cc/commit/d03f7ae79ddda0ad228b17048b9e2dc0efcc8e95
 #