build: modern_project_structure.cmake added

cmake/modern_project_structure.cmake

@@ -0,0 +1,31 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2018 Mateusz Pusz
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+cmake_minimum_required(VERSION 3.4)
+
+function(ensure_entry_point)
+  if(NOT CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+      message(FATAL_ERROR "'${CMAKE_CURRENT_SOURCE_DIR}/CMakeLists.txt' is meant to be used only "
+              "as a CMake entry point and should not be included from other CMake files. "
+              "Include '${CMAKE_CURRENT_SOURCE_DIR}/src/CMaskeLists.txt' directly instead.")
+  endif()
+endfunction()