[CI] Fix llvm-lit path for LLVM 23 apt packages (#3620)

The `llvm-X-tools` apt package previously shipped `lit` as a Python
script at `build/utils/lit/lit.py`.
This path was removed in the Debian/Ubuntu packaging of LLVM 23:
["Install a lit
binary"](https://salsa.debian.org/pkg-llvm-team/llvm-toolchain/-/commit/bedcb23bc00c9fe407725803d73e50ec6c8ecaf9)

The packaging now installs a compiled `lit` binary at `bin/lit` instead,
with a `/usr/bin/lit-X` symlink.
Updated LLVM_EXTERNAL_LIT` to match the new location.

Author: vmaksimo

.github/workflows/check-out-of-tree-build.yml

@@ -98,7 +98,7 @@ jobs:
             -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} \
             -DCMAKE_CXX_FLAGS="-Werror" \
             -DLLVM_INCLUDE_TESTS=ON \
-            -DLLVM_EXTERNAL_LIT="/usr/lib/llvm-${{ env.LLVM_VERSION }}/build/utils/lit/lit.py" \
+            -DLLVM_EXTERNAL_LIT="/usr/lib/llvm-${{ env.LLVM_VERSION }}/bin/lit" \
             -DLLVM_EXTERNAL_SPIRV_HEADERS_SOURCE_DIR=${{ github.workspace }}/SPIRV-Headers \
             -G "Unix Makefiles"
       - name: Build
@@ -109,3 +109,4 @@ jobs:
         run: |
           cd build
           make check-llvm-spirv -j$(nproc)
+