Fix HDF5 version checking

cmake/FindHDF5.cmake

@@ -4,7 +4,7 @@
 #------------------------------------------------------------------------------#
 
 # This module is already included in new versions of CMake
-if(CMAKE_VERSION VERSION_LESS 3.9)
+if(CMAKE_VERSION VERSION_LESS 3.10)
   include(${CMAKE_CURRENT_LIST_DIR}/upstream/FindHDF5.cmake)
 else()
   include(${CMAKE_ROOT}/Modules/FindHDF5.cmake)

cmake/upstream/FindHDF5.cmake

@@ -214,7 +214,7 @@ function(_HDF5_test_regular_compiler_C success version is_parallel)
     )
     set(${version} ${CMAKE_MATCH_1})
     if(CMAKE_MATCH_3)
-      set(${version} ${HDF5_CXX_VERSION}.${CMAKE_MATCH_3})
+      set(${version} ${${version}}.${CMAKE_MATCH_3})
     endif()
     set(${version} ${${version}} PARENT_SCOPE)
 
@@ -262,7 +262,7 @@ function(_HDF5_test_regular_compiler_CXX success version is_parallel)
     )
     set(${version} ${CMAKE_MATCH_1})
     if(CMAKE_MATCH_3)
-      set(${version} ${HDF5_CXX_VERSION}.${CMAKE_MATCH_3})
+      set(${version} ${${version}}.${CMAKE_MATCH_3})
     endif()
     set(${version} ${${version}} PARENT_SCOPE)