fix: zstd cmake_minimum_required is 2.8, but not supported anymore

we don't want to bump zstd to latest just yet as it changes the
compressed hash of a message, and we are not sure what would happen with
libsession

Author: Bilb

CMakeLists.txt

@@ -43,6 +43,7 @@ endif()
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
+set(CMAKE_POLICY_VERSION_MINIMUM 3.5)
 
 set(default_static_libstd OFF)
 if(WIN32)