chore(ci): add installation step for LLVM 18

bindgen requires Clang 9 and above. Add the libclang-dev and clang
packages from LLVM 18 toolchain.

Author: jorge-ortega

.github/workflows/rust.yml

@@ -80,7 +80,7 @@ jobs:
           sudo apt-get install -y libssl-dev
           sudo apt-get install -y libcurl4-openssl-dev
 
-      - name: Install LLVM 7
+      - name: Install LLVM 7 (for NVVM backend)
         if: contains(matrix.os, 'ubuntu')
         run: |
           mkdir -p ~/llvm7 && cd ~/llvm7
@@ -92,6 +92,15 @@ jobs:
           sudo apt-get install -y ./*.deb
           sudo ln -s /usr/bin/llvm-config-7 /usr/local/bin/llvm-config
 
+      - name: Install LLVM 18 (for bindgen)
+        if: contains(matrix.os, 'ubuntu')
+        run: |
+          mkdir -p ~/llvm18 && cd ~/llvm18
+          wget https://mirrors.kernel.org/ubuntu/pool/universe/l/llvm-toolchain-18/libclang-18-dev_18.1.8-17_amd64.deb
+          sudo apt-get update
+          sudo apt-get install -y ./*.deb
+          export LIBCLANG_PATH=/usr/lib/llvm-18/lib
+
       - name: Load Rust Cache
         uses: Swatinem/[email protected]
         with: