[cmake] Deprecate message_verbose

CHANGELOG.md

@@ -95,6 +95,10 @@ In order to build the DUNE core modules you need at least the following software
 - The cmake options `CXX_MAX_STANDARD`, `CXX_MAX_SUPPORTED_STANDARD` and `DISABLE_CXX_VERSION_CHECK`
   are removed. The cmake function `dune_require_cxx_standard()` is now deprecated.
 
+- Deprecate CMake macro `message_verbose`. Use `message(VERBOSE "message text")` instead.
+  This macro will be removed after Dune 2.10.
+
+
 ## Deprecations and removals
 
 - The deprecated header `dune/common/function.hh` has been removed. Use C++ function

cmake/modules/DuneInstance.cmake

@@ -469,13 +469,15 @@
 include_guard(GLOBAL)
 
 # macro to print additional information to the cmake output file.
-# Note: in cmake 3.15 this is available through the message(VERBOSE "...") function.
+#
+# .. deprecated:: 2.10
+#
+# Use `message(VERBOSE "message text")` instead. This macro will be
+# removed after Dune 2.10.
 macro(message_verbose TEXT)
-  if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.15")
-    message(VERBOSE "${TEXT}")
-  else()
-    file(APPEND ${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log "${TEXT}\n")
-  endif()
+  message(VERBOSE "${TEXT}")
+
+  message(DEPRECATION "message_verbose is deprecated, use directly message(VERBOSE \"message text\")")
 endmacro(message_verbose)