Zstd: Change package status to recommended

cmake/LinkPackage.cmake

@@ -1,5 +1,5 @@
 function(link_package NAME)
-    cmake_parse_arguments(LP "ENCOURAGED" "TARGET" "" ${ARGN})
+    cmake_parse_arguments(LP "ENCOURAGED;RECOMMENDED" "TARGET" "" ${ARGN})
 
     if(${NAME}_FOUND)
         string(TOUPPER "${NAME}" UCNAME)
@@ -19,5 +19,7 @@ function(link_package NAME)
         endif()
     elseif(LP_ENCOURAGED)
         message(WARNING "${NAME} not found; compiling OpenTTD without ${NAME} is strongly disencouraged")
+    elseif(LP_RECOMMENDED)
+        message(WARNING "${NAME} not found; compiling OpenTTD without ${NAME} is not recommended")
     endif()
 endfunction()