USER-QUIP.cmake: create and use imported target

cmake/Modules/FindQUIP.cmake

@@ -7,12 +7,21 @@
 
 find_library(QUIP_LIBRARY NAMES quip)
 
-set(QUIP_LIBRARIES ${QUIP_LIBRARY})
-
 include(FindPackageHandleStandardArgs)
 # handle the QUIETLY and REQUIRED arguments and set QUIP_FOUND to TRUE
 # if all listed variables are TRUE
 
 find_package_handle_standard_args(QUIP DEFAULT_MSG QUIP_LIBRARY)
 
+# Copy the results to the output variables and target.
+if(QUIP_FOUND)
+  set(QUIP_LIBRARIES ${QUIP_LIBRARY})
+
+  if(NOT TARGET QUIP::QUIP)
+    add_library(QUIP::QUIP UNKNOWN IMPORTED)
+    set_target_properties(QUIP::QUIP PROPERTIES
+      IMPORTED_LOCATION "${QUIP_LIBRARY}")
+  endif()
+endif()
+
 mark_as_advanced(QUIP_LIBRARY)

cmake/Modules/Packages/USER-QUIP.cmake

@@ -1,5 +1,5 @@
 if(PKG_USER-QUIP)
   enable_language(Fortran)
   find_package(QUIP REQUIRED)
-  target_link_libraries(lammps PRIVATE ${LAPACK_LIBRARIES})
+  target_link_libraries(lammps PRIVATE QUIP::QUIP ${LAPACK_LIBRARIES})
 endif()