Current CMake removed the OLD behavior of CMP0020.

diff -Nrup a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt	2016-11-29 16:44:51.000000000 +0100
+++ b/CMakeLists.txt	2026-10-22 17:22:14.842928388 +0200
@@ -8,7 +8,6 @@ CMAKE_POLICY(SET CMP0003 NEW)
 
 # Do not link against qtmain on Windows
 if(POLICY CMP0020)
-	cmake_policy(SET CMP0020 OLD)
 endif()
 
 set(CMAKE_INSTALL_NAME_DIR ${LIB_INSTALL_DIR})