Install ARM toolchain v15.2 from official source

Replace apt-installed gcc-arm-none-eabi with ARM GNU Toolchain 15.2.rel1 downloaded directly from developer.arm.com to get a more recent and controlled toolchain version.

Author: vanvught

.github/workflows/c-cpp.yml

@@ -20,8 +20,15 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: '3.10'
-    - name: Install arm-none-eabi
-      run: sudo apt install gcc-arm-none-eabi
+    - name: Install arm-none-eabi v15
+      run: |
+        set -e
+        TOOLCHAIN_URL="https://developer.arm.com/-/media/Files/downloads/gnu/15.2.rel1/binrel/arm-gnu-toolchain-15.2.rel1-x86_64-arm-none-eabi.tar.xz"
+        TOOLCHAIN_DIR="/opt/arm-gnu-toolchain-15.2.rel1-x86_64-arm-none-eabi"
+        sudo mkdir -p /opt
+        wget -qO /tmp/arm-toolchain.tar.xz "$TOOLCHAIN_URL"
+        sudo tar -xJf /tmp/arm-toolchain.tar.xz -C /opt
+        echo "$TOOLCHAIN_DIR/bin" >> "$GITHUB_PATH"
     - name: version
       run: arm-none-eabi-g++ --version
     - name: make bootloader-tftp