add H5CPP_OLD_CMAKE switch (#697)

Author: jkotan

.github/workflows/cmake-build.yml

@@ -295,7 +295,7 @@ jobs:
         run: |
           docker  exec  --user root build  /bin/bash -c "chown -R p00user /home/p00user/src"
           docker  exec build /bin/bash -c "HDF5_STATIC=ON; [ \"${H5CPP_SHARED}\" = \"True\" ] && HDF5_STATIC=OFF; git config --global --add safe.directory /home/p00user/src && mkdir ../build &&  cd ../build &&
-          cmake ../src -DCMAKE_BUILD_TYPE=Release -DH5CPP_CONAN=DISABLE -DH5CPP_CATCH2_V2=TRUE -DHDF5_USE_STATIC_LIBRARIES=${HDF5_STATIC} -DH5CPP_BUILD_SHARED=${H5CPP_SHARED}  -DH5CPP_WITH_BOOST=${H5CPP_WITH_BOOST} -DH5CPP_WITH_MPI=${H5CPP_WITH_MPI}"
+          cmake ../src -DCMAKE_BUILD_TYPE=Release -DH5CPP_CONAN=DISABLE -DH5CPP_OLD_CMAKE=ON -DH5CPP_CATCH2_V2=TRUE -DHDF5_USE_STATIC_LIBRARIES=${HDF5_STATIC} -DH5CPP_BUILD_SHARED=${H5CPP_SHARED}  -DH5CPP_WITH_BOOST=${H5CPP_WITH_BOOST} -DH5CPP_WITH_MPI=${H5CPP_WITH_MPI}"
       - name: Build all
         run: docker  exec build /bin/bash -c "cd ../build &&  cmake --build . -- -j 2"
       - name: Build html

CMakeLists.txt

@@ -6,13 +6,19 @@ project(h5cpp
       VERSION 0.7
     )
 
+option(H5CPP_OLD_CMAKE "enable support for old cmake versions" OFF)
 
 #=============================================================================
 # Augment CMake with our custom scripts
 #=============================================================================
 set(EXTRA_MODULES_DIR ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 list(APPEND CMAKE_MODULE_PATH ${EXTRA_MODULES_DIR})
 
+if (H5CPP_OLD_CMAKE)
+  set(EXTRA_OLDMODULES_DIR ${CMAKE_CURRENT_SOURCE_DIR}/cmake/old)
+  list(APPEND CMAKE_MODULE_PATH ${EXTRA_OLDMODULES_DIR})
+endif()
+
 if (NOT DEFINED BUILD_SHARED_LIBS)
   set(BUILD_SHARED_LIBS ON)
 endif()
@@ -171,10 +177,12 @@ install(FILES
     DESTINATION ${CMAKE_INSTALL_PACKAGEDIR}
     COMPONENT development)
 
-install(FILES
-        cmake/FindHDF5.cmake
-        DESTINATION ${CMAKE_INSTALL_PACKAGEDIR}/hdf5
-        COMPONENT development)
+if (H5CPP_OLD_CMAKE)
+  install(FILES
+    cmake/old/FindHDF5.cmake
+    DESTINATION ${CMAKE_INSTALL_PACKAGEDIR}/hdf5
+    COMPONENT development)
+endif()
 
 #
 # uninstall target