add comment about CMAKE policy

Author: tomjunk

CMakeLists.txt

@@ -16,6 +16,13 @@
 cmake_minimum_required (VERSION 3.20 FATAL_ERROR)
 # cmake_policy(VERSION 3.18)
 
+# See https://cmake.org/cmake/help/latest/policy/CMP0048.html#policy:CMP0048
+# as of Feb 2026, dunesw mrb-built products set the version in the
+# CMAKE_PROJECT_VERSION_STRING set, and not in the project line.
+# but we must be using the OLD policy.  Setting the version string
+# here will get overwritten by the project line with the same value when
+# we migrate to the NEW policy
+
 set(PROJECT_VERSION 03.12.00)
 project(duneanaobj VERSION ${PROJECT_VERSION} LANGUAGES CXX)
 set(${PROJECT_NAME}_CMAKE_PROJECT_VERSION_STRING ${PROJECT_VERSION})