message: Ensure tests are always compiled with C++14.
diff: @@ -3,6 +3,7 @@ function(ginkgo_create_test test_name)
  ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
  string(REPLACE "/" "_" TEST_TARGET_NAME "${REL_BINARY_DIR}/${test_name}")
  add_executable(${TEST_TARGET_NAME} ${test_name}.cpp)
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  target_include_directories("${TEST_TARGET_NAME}"
  PRIVATE
  "$<BUILD_INTERFACE:${Ginkgo_BINARY_DIR}>"
  @@ -23,6 +24,7 @@ function(ginkgo_create_thread_test test_name)
  ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
  string(REPLACE "/" "_" TEST_TARGET_NAME "${REL_BINARY_DIR}/${test_name}")
  add_executable(${TEST_TARGET_NAME} ${test_name}.cpp)
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  target_include_directories("${TEST_TARGET_NAME}"
  PRIVATE
  "$<BUILD_INTERFACE:${Ginkgo_BINARY_DIR}>"
  @@ -41,6 +43,7 @@ function(ginkgo_create_test_cpp_cuda_header test_name)
  ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
  string(REPLACE "/" "_" TEST_TARGET_NAME "${REL_BINARY_DIR}/${test_name}")
  add_executable(${TEST_TARGET_NAME} ${test_name}.cpp)
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  target_include_directories("${TEST_TARGET_NAME}"
  PRIVATE
  "$<BUILD_INTERFACE:${Ginkgo_BINARY_DIR}>"
  @@ -60,6 +63,7 @@ function(ginkgo_create_cuda_test test_name)
  ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
  string(REPLACE "/" "_" TEST_TARGET_NAME "${REL_BINARY_DIR}/${test_name}")
  add_executable(${TEST_TARGET_NAME} ${test_name}.cu)
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  target_include_directories("${TEST_TARGET_NAME}"
  PRIVATE
  "$<BUILD_INTERFACE:${Ginkgo_BINARY_DIR}>"
  @@ -80,6 +84,7 @@ function(ginkgo_create_hip_test_special_linkage test_name)
  ${PROJECT_BINARY_DIR} ${CMAKE_CURRENT_BINARY_DIR})
  string(REPLACE "/" "_" TEST_TARGET_NAME "${REL_BINARY_DIR}/${test_name}")
  add_executable(${TEST_TARGET_NAME} ${test_name}.cpp)
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  # Fix the missing metadata when building static library.
  if(GINKGO_HIP_PLATFORM MATCHES "hcc" AND NOT BUILD_SHARED_LIBS)
  set_target_properties(${TEST_TARGET_NAME} PROPERTIES LINKER_LANGUAGE HIP)
  @@ -116,6 +121,7 @@ function(ginkgo_create_hip_test test_name)
  NVCC_OPTIONS ${GINKGO_HIP_NVCC_OPTIONS}
  HCC_OPTIONS ${GINKGO_HIP_HCC_OPTIONS})
  endif()
  + target_compile_features("${TEST_TARGET_NAME}" PUBLIC cxx_std_14)
  # Let's really not use nvcc for linking here
  if (GINKGO_HIP_PLATFORM MATCHES "nvcc")
  