CMakeLIsts.txt + comment to explain CMP0177 OLD

CMakeLists.txt

@@ -6,13 +6,21 @@
 
 cmake_minimum_required(VERSION 3.20 FATAL_ERROR)
 if (CMAKE_VERSION GREATER_EQUAL 3.30)
-   cmake_policy(SET CMP0167 OLD)
+    cmake_policy(SET CMP0167 OLD)
+    # Old policy uses FindBoost.cmake provided by CMake, which is deprecated.
+    # New policy uses BoostConfig.cmake provided by Boost.  It returns targets
+    # Boost::ProgramOptions etc instead of library paths.  We still have to find
+    # out how replace the configure_file command in MakePythonWheel.cmake.
+    # See https://jugit.fz-juelich.de/mlz/bornagain/-/issues/1074.
 endif()
 if (CMAKE_VERSION GREATER_EQUAL 3.31)
-   cmake_policy(SET CMP0175 NEW)
+    cmake_policy(SET CMP0175 NEW)
 endif()
 if (CMAKE_VERSION GREATER_EQUAL 3.31)
-   cmake_policy(SET CMP0177 OLD)
+    cmake_policy(SET CMP0177 OLD)
+    # New behavior, introduced in CMake 3.31, normalizes all DESTINATION values
+    # given in any form of the install() command.
+    # Conversion to NEW behavior postponed until we require CMake >= 3.31.
 endif()
 
 set(CMAKE_MODULE_PATH