docs: replace git command line argument for target check-git

- --compact-summary is not available with the standard
    git installation on CentOS 7
- in contrast --stat is already available with git 1.8.2

docs/manuals/CMakeLists.txt

@@ -62,7 +62,7 @@ add_custom_target( clean-docs
 # this target checks if the generated json files differ from the ones in the repository.
 
 add_custom_target ( check-git
-  COMMAND git diff --exit-code --compact-summary ${PROJECT_SOURCE_DIR}/source/include/autogenerated
+  COMMAND git diff --exit-code --stat=80 ${PROJECT_SOURCE_DIR}/source/include/autogenerated
   DEPENDS ${AUTOGENERATED_RESOURCE_DESCRIPTION_JSON_FILES}
   WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
   COMMENT "Comparing json files in \"${PROJECT_SOURCE_DIR}/source/include/autogenerated\" with git repo" )