Extend small_world with llvm20

Author: martin4861

examples/small_world/.bazelrc

@@ -1,5 +1,7 @@
 common --@rules_swiftnav//cc:enable_bzlmod=true
 
+build:aarch64_darwin_llvm20 --platforms @rules_swiftnav//platforms:aarch64_darwin_llvm20
+
 coverage --experimental_generate_llvm_lcov
 coverage --combined_report=lcov
 

examples/small_world/MODULE.bazel

@@ -10,6 +10,7 @@ local_path_override(
 swift_cc_toolchain_ext = use_extension("@rules_swiftnav//cc:extensions.bzl", "swift_cc_toolchain_extension")
 use_repo(
     swift_cc_toolchain_ext,
+    "aarch64-darwin-llvm",
     "aarch64-darwin-llvm20",
     "aarch64-linux-llvm20",
     "aarch64-sysroot",
@@ -19,6 +20,7 @@ use_repo(
 )
 
 register_toolchains(
+    "@rules_swiftnav//cc/toolchains/llvm/aarch64-darwin:cc-toolchain-aarch64-darwin",
     "@rules_swiftnav//cc/toolchains/llvm20/aarch64-darwin:cc-toolchain-aarch64-darwin",
     "@rules_swiftnav//cc/toolchains/llvm20/x86_64-darwin:cc-toolchain-x86_64-darwin",
     "@rules_swiftnav//cc/toolchains/llvm20/aarch64-linux:cc-toolchain-aarch64-linux",