btf: re-enable host dd fix for hermetic BTF generation

Run 31243889436 got past resolve_btfids building (0001+0002 working)
and reached the vmlinux link, where gen_btf in link-vmlinux.sh:253 died
with 'dd: not found' because the hermetic PATH has no coreutils.
Re-enable the step that echoes ADDITIONAL_HOST_TOOLS=dd into
build.config.gki.aarch64 so the hermetic host_tools dir contains dd.

.github/actions/btf/action.yml

@@ -72,7 +72,7 @@ runs:
     - name: Expose host dd for hermetic BTF generation (android12-5.10)
       shell: bash
       working-directory: ${{ github.workspace }}/kernel/common
-      if: false
+      if: ${{ inputs.version == 'android12-5.10' }}
       run: |
         set -euo pipefail
         # The hermetic toolchain PATH (build.config.common -> HERMETIC_TOOLCHAIN=1)