FindHDF5: List imported targets in debug output

If HDF5_FIND_DEBUG, list all targets that are defined
(from either FindHDF5.cmake or the hdf5-config.cmake).

Modules/FindHDF5.cmake

@@ -1154,6 +1154,21 @@ if (HDF5_FIND_DEBUG)
     message(STATUS "HDF5_${_lang}_HL_LIBRARY: ${HDF5_${_lang}_HL_LIBRARY}")
     message(STATUS "HDF5_${_lang}_HL_LIBRARIES: ${HDF5_${_lang}_HL_LIBRARIES}")
   endforeach()
+  message(STATUS "Defined targets (if any):")
+  foreach(_lang IN  ITEMS "" "_cpp" "_fortran")
+    foreach(_hl IN  ITEMS "" "_hl")
+      foreach(_prefix IN ITEMS "hdf5::" "")
+        foreach(_suffix IN ITEMS "-static" "-shared" "")
+          set (_target ${_prefix}hdf5${_hl}${_lang}${_suffix})
+          if (TARGET  ${_target})
+            message(STATUS "... ${_target}")
+          else()
+            #message(STATUS "... ${_target} does not exist")
+          endif()
+        endforeach()
+      endforeach()
+    endforeach()
+  endforeach()
 endif()
 unset(_lang)
 unset(_HDF5_NEED_TO_SEARCH)