qt4: add missing libSM dependency (#17611)
qt4: add missing libSM dependency (#17611)

See https://github.com/spack/spack/issues/15082 and
https://github.com/spack/spack/pull/16226
iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,iulian787/spack,iulian787/spack,LLNL/spack,LLNL/spack,LLNL/spack