Fix compilation on CentOS 7 (missing link to libdl) (#2849)

Co-authored-by: Paul Romano <paul.k.romano@gmail.com>

CMakeLists.txt

@@ -497,7 +497,7 @@ endif()
 # target_link_libraries treats any arguments starting with - but not -l as
 # linker flags. Thus, we can pass both linker flags and libraries together.
 target_link_libraries(libopenmc ${ldflags} ${HDF5_LIBRARIES} ${HDF5_HL_LIBRARIES}
-                      xtensor gsl::gsl-lite-v1 fmt::fmt)
+                      xtensor gsl::gsl-lite-v1 fmt::fmt ${CMAKE_DL_LIBS})
 
 if(TARGET pugixml::pugixml)
   target_link_libraries(libopenmc pugixml::pugixml)