cmake: fix linking again plumed

  if(DOWNLOAD_PLUMED)

    include(ExternalProject)

    ExternalProject_Add(plumed_build

      URL https://github.com/plumed/plumed2/releases/download/v2.4.3/plumed-2.4.3.tgz 

      URL_MD5 bed9c88c8c635b269c1cd4a0598a2934

      URL https://github.com/plumed/plumed2/releases/download/v2.4.3/plumed-src-2.4.3.tgz 

      URL_MD5 b1be7c48971627febc11c61b70767fc5

      BUILD_IN_SOURCE 1

      CONFIGURE_COMMAND <SOURCE_DIR>/configure --prefix=<INSTALL_DIR> 

                                               $<$<BOOL:${BUILD_SHARED_LIBS}>:--with-pic>                                                  )

    ExternalProject_get_property(plumed_build INSTALL_DIR)

    set(PLUMED_INSTALL_DIR ${INSTALL_DIR})

    list(APPEND LAMMPS_DEPS plumed_build)

    list(APPEND LAMMPS_LINK_LIBS ${PLUMED_INSTALL_DIR}/lib/libplumed.so)

    list(APPEND LAMMPS_LINK_LIBS ${PLUMED_INSTALL_DIR}/lib/libplumedWrapper.a ${CMAKE_DL_LIBS})

    set(PLUMED_INCLUDE_DIRS "${PLUMED_INSTALL_DIR}/include")

  else()

    find_package(PkgConfig REQUIRED)

    pkg_check_modules(PLUMED plumed REQUIRED)

    pkg_check_modules(PLUMED plumedWrapper REQUIRED)

    list(APPEND LAMMPS_LINK_LIBS ${PLUMED_LDFLAGS})

  endif()

  include_directories(${PLUMED_INCLUDE_DIRS})