[gn build] Fix per target runtime directory path

[paulkirth]

oops, did arc diff on main instead of my branch.

llvm/utils/gn/secondary/clang/runtimes.gni

 import("//clang/resource_dir.gni")
 import("//llvm/triples.gni")
 
 declare_args() {
   # Use target triple as the name of the runtimes directory.
   clang_enable_per_target_runtime_dir = false
 }
 
 if (clang_enable_per_target_runtime_dir) {
-  runtimes_dir = "$clang_resource_dir/$llvm_target_triple/lib"
+  runtimes_dir = "$clang_resource_dir/lib/$llvm_target_triple"
 } else {
   runtimes_dir = "$root_build_dir/lib"
 }