pw_toolchain: Use new CIPD GN variables

Bug: b/240726250
Change-Id: Ia5e4404288f43ae854011b45191c8fe59102fa1f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/104283
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

pw_toolchain/host_clang/BUILD.gn

@@ -114,7 +114,7 @@ config("xcode_sysroot") {
 # Pull the appropriate paths from our Pigweed env setup.
 config("no_system_libcpp") {
  if (current_os == "mac") {
- install_dir = dir_cipd_pigweed
+ install_dir = pw_env_setup_CIPD_PIGWEED
  assert(install_dir != "",
  "You forgot to activate the Pigweed environment; " +
  "did you source pw_env_setup/setup.sh?")
@@ -123,7 +123,7 @@ config("no_system_libcpp") {
  "-nostdlib++",
 
  # Use the libc++ from CIPD.
- rebase_path(dir_cipd_pigweed + "/lib/libc++.a", root_build_dir),
+ rebase_path(pw_env_setup_CIPD_PIGWEED + "/lib/libc++.a", root_build_dir),
  ]
  }
 }