Add @rules_hdl to matcha airgap tarball

Bypass-Presubmit-Reason: no presubmits, tested manually
Change-Id: I76d6647ec79bf14c31c3e16e8722365512341b43

util/prep-bazel-airgapped-build.sh

diff --git a/util/prep-bazel-airgapped-build.sh b/util/prep-bazel-airgapped-build.sh
index 0728b97..ba99c9d 100755
--- a/util/prep-bazel-airgapped-build.sh
+++ b/util/prep-bazel-airgapped-build.sh
@@ -185,6 +185,13 @@
     mkdir -p ${ROOTDIR}/out/kelvin/hw/kelvin_core
     touch ${ROOTDIR}/out/kelvin/hw/kelvin_core/kelvin.core
   fi
+  # bazel needs these dirs, even if they are empty
+  if [[ ! -f "${ROOTDIR}/cache/toolchain_kelvin" ]]; then
+    mkdir -p ${ROOTDIR}/cache/toolchain_kelvin
+  fi
+  if [[ ! -f "${ROOTDIR}/cache/cheriot_tools" ]]; then
+    mkdir -p ${ROOTDIR}/cache/cheriot_tools
+  fi
   # Patch airgap build environment
   git apply util/bazel_airgapped.patch
   # Make bazel forget everything it knows, then download everything.
@@ -202,6 +209,7 @@
     @python3_toolchains//... \
     @remotejdk11_linux//... \
     @rules_foreign_cc//toolchains/... \
+    @rules_hdl//:all \
     @rust_analyzer_1.67.0_tools//... \
     @rust_linux_x86_64__x86_64-unknown-linux-gnu__nightly_tools//... \
     @org_chipsalliance_chisel_plugin//... \