Update cpp.yml

[indy256]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the Ubuntu LLVM toolchain from Clang 20 to Clang 21 in the CI workflow.

• Switches the apt repository from llvm-toolchain-focal-20 to llvm-toolchain-noble for Clang 21
• Updates the compile commands to install and invoke clang-21 instead of clang-20

Comments suppressed due to low confidence (2)

.github/workflows/cpp.yml:36

• The Ubuntu codename 'noble' may not be supported by apt.llvm.org for the Clang toolchain. Verify that this distribution exists on apt.llvm.org or use a valid codename (e.g., 'jammy' or 'mantic').

sudo add-apt-repository "deb http://apt.llvm.org/noble/ llvm-toolchain-noble main"

.github/workflows/cpp.yml:37

• [nitpick] Clang version '21' is hard-coded in multiple steps; consider defining the version as a single variable or workflow input to simplify future upgrades.

sudo apt-get install clang-21