ci: clang: Use LLVM_TOOLCHAIN_PATH instead of CLANG_ROOT_DIR

`CLANG_ROOT_DIR` is deprecated; use `LLVM_TOOLCHAIN_PATH` instead.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

.github/workflows/clang.yaml

@@ -24,7 +24,7 @@ jobs:
         platform: ["native_posix"]
     env:
       ZEPHYR_SDK_INSTALL_DIR: /opt/toolchains/zephyr-sdk-0.15.0
-      CLANG_ROOT_DIR: /usr/lib/llvm-12
+      LLVM_TOOLCHAIN_PATH: /usr/lib/llvm-12
       COMMIT_RANGE: ${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }}
       BASE_REF: ${{ github.base_ref }}
     outputs:
@@ -69,7 +69,7 @@ jobs:
       - name: Check Environment
         run: |
           cmake --version
-          ${CLANG_ROOT_DIR}/bin/clang --version
+          ${LLVM_TOOLCHAIN_PATH}/bin/clang --version
           gcc --version
           ls -la