Update apple release_name for version >= 18 (#382)

As shown in commit 6c57c24, the newer
apple releases seem to use `apple-macos11` instead of
`apple-darwin22.0`. (Though I am not sure what would be used for x86,
since I can't find such a build for llvm version >= 18.)

Also, if this is merged, can we get a new toolchains_llvm release
(v1.1.3) shortly after? The most recent apple binary currently available
in v1.1.2 is quite old.

Author: Danielkonge

toolchain/internal/release_name.bzl

@@ -27,11 +27,16 @@ def _darwin_apple_suffix(llvm_version, arch):
             return "apple-darwin21.0"
         else:
             return "apple-darwin"
-    elif major_llvm_version >= 15:
+    elif major_llvm_version >= 15 and major_llvm_version < 18:
         if arch == "arm64":
             return "apple-darwin22.0"
         else:
             return "apple-darwin21.0"
+    elif major_llvm_version >= 18:
+        if arch == "arm64":
+            return "apple-macos11"
+        else:
+            return "apple-darwin21.0"
     else:
         return "apple-darwin"