fix(cublas): check for .h in subdirs when copying non-standard include dirs

ls *.h missed headers in subdirectories like crt/host_defines.h;
use find -maxdepth 2 instead.

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

iso/builder/build-cublas.sh

@@ -125,7 +125,7 @@ copy_headers() {
         case "$inc_dir" in
             */usr/include) ;;  # already handled above
             *)
-                if ls "${inc_dir}"/*.h > /dev/null 2>&1; then
+                if find "${inc_dir}" -name '*.h' -maxdepth 2 | grep -q .; then
                     cp -a "${inc_dir}/." "${CACHE_DIR}/include/"
                 fi
                 ;;