Remove the temporary directory after extracting buildkit (#874)

Author: IDisposable

.devcontainer/install-deps.sh

@@ -32,4 +32,5 @@ wget https://github.com/jetkvm/rv1106-system/releases/download/${BUILDKIT_VERSIO
     sudo mkdir -p /opt/jetkvm-native-buildkit && \
     sudo tar --use-compress-program="unzstd --long=31" -xvf buildkit.tar.zst -C /opt/jetkvm-native-buildkit && \
     rm buildkit.tar.zst
-popd
+popd
+rm -rf "${BUILDKIT_TMPDIR}"