Use PkgConfig to find Zstd

# Find Zstd library

#

#  Zstd_INCLUDE_DIRS - where to find zstd.h, etc.

#  Zstd_LIBRARIES    - List of libraries when using libzstd

#  Zstd_FOUND        - True if libzstd is found.

find_path(Zstd_INCLUDE_DIR NAMES zstd.h)

find_library(Zstd_LIBRARY NAMES zstd)

# handle the QUIET and REQUIRED arguments and

# set Zstd_FOUND to TRUE if all variables are non-zero

include(FindPackageHandleStandardArgs)

find_package_handle_standard_args(Zstd DEFAULT_MSG Zstd_LIBRARY Zstd_INCLUDE_DIR)

# Copy the results to the output variables and target.

if(Zstd_FOUND)

  set(Zstd_LIBRARIES ${Zstd_LIBRARY})

  set(Zstd_INCLUDE_DIRS ${Zstd_INCLUDE_DIR})

  if(NOT TARGET Zstd::Zstd)

    add_library(Zstd::Zstd UNKNOWN IMPORTED)

    set_target_properties(Zstd::Zstd PROPERTIES

      IMPORTED_LOCATION "${Zstd_LIBRARY}"

      INTERFACE_INCLUDE_DIRECTORIES "${Zstd_INCLUDE_DIR}")

  endif()

endif()

mark_as_advanced(Zstd_INCLUDE_DIR Zstd_LIBRARY)

find_package(ZLIB REQUIRED)

target_link_libraries(lammps PRIVATE ZLIB::ZLIB)

find_package(Zstd)

find_package(PkgConfig REQUIRED)

pkg_check_modules(Zstd IMPORTED_TARGET libzstd)

if(Zstd_FOUND)

    target_compile_definitions(lammps PRIVATE -DLAMMPS_ZSTD)

    target_link_libraries(lammps PRIVATE Zstd::Zstd)

    target_link_libraries(lammps PRIVATE PkgConfig::Zstd)

endif()