Set CMake policy 0077 for easy inclusion from other CMake prjs (pantor#262)

Co-authored-by: Bren de Hartog <[email protected]>

Author: hartogjr

CMakeLists.txt

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION 3.5)
 
+# See https://cmake.org/cmake/help/latest/policy/CMP0077.html
+# This allows for setting option variables externally, when this project
+# is included in another CMake project.
+cmake_policy(SET CMP0077 NEW)
 
 project(inja LANGUAGES CXX VERSION 3.4.0)