FindHDF5: recognize hdf5:: prefix when using hdf5-config.cmake

Some versions of HDF5 use this prefix on their imported targets.

Modules/FindHDF5.cmake

@@ -404,12 +404,16 @@ if(NOT HDF5_FOUND)
         set(HDF5_IS_PARALLEL ${HDF5_ENABLE_PARALLEL})
         set(HDF5_INCLUDE_DIRS ${HDF5_INCLUDE_DIR})
         set(HDF5_LIBRARIES)
-        set(HDF5_C_TARGET hdf5)
-        set(HDF5_C_HL_TARGET hdf5_hl)
-        set(HDF5_CXX_TARGET hdf5_cpp)
-        set(HDF5_CXX_HL_TARGET hdf5_hl_cpp)
-        set(HDF5_Fortran_TARGET hdf5_fortran)
-        set(HDF5_Fortran_HL_TARGET hdf5_hl_fortran)
+        if (NOT TARGET hdf5 AND NOT TARGET hdf5-static AND NOT TARGET hdf5-shared)
+            # Some HDF5 versions (e.g. 1.8.18) used hdf5::hdf5 etc
+            set(_target_prefix "hdf5::")
+        endif()
+        set(HDF5_C_TARGET ${_target_prefix}hdf5)
+        set(HDF5_C_HL_TARGET ${_target_prefix}hdf5_hl)
+        set(HDF5_CXX_TARGET ${_target_prefix}hdf5_cpp)
+        set(HDF5_CXX_HL_TARGET ${_target_prefix}hdf5_hl_cpp)
+        set(HDF5_Fortran_TARGET ${_target_prefix}hdf5_fortran)
+        set(HDF5_Fortran_HL_TARGET ${_target_prefix}hdf5_hl_fortran)
         if(HDF5_USE_STATIC_LIBRARIES)
             set(_suffix "-static")
         else()