fix(cublas): search all include/ dirs in deb for CUDA headers

NVIDIA CUDA .deb packages install headers under
/usr/local/cuda-X.Y/targets/x86_64-linux/include/ not /usr/include/,
causing copy_headers() to silently skip them.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/build-cublas.sh

@@ -119,6 +119,17 @@ copy_headers() {
     if [ -d "${from}/usr/include" ]; then
         cp -a "${from}/usr/include/." "${CACHE_DIR}/include/"
     fi
+    # NVIDIA CUDA packages install headers under /usr/local/cuda-X.Y/targets/x86_64-linux/include/
+    find "$from" -type d -name include | while read -r inc_dir; do
+        case "$inc_dir" in
+            */usr/include) ;;  # already handled above
+            *)
+                if ls "${inc_dir}"/*.h > /dev/null 2>&1; then
+                    cp -a "${inc_dir}/." "${CACHE_DIR}/include/"
+                fi
+                ;;
+        esac
+    done
 }
 
 copy_libs() {