message: build: simplify the condition in the repl build (NFC)
  Fold a `if(cond)` followed with an `if(NOT cond)` set into a single set.
  NFC.
diff: @@ -28,8 +28,7 @@ if(MSVC)
  # disable inline function expansion so that we have a function that we can
  # break upon
  target_compile_options(repl_swift PRIVATE /Ob0)
  -endif()
  -if(NOT MSVC)
  +else()
  set_target_properties(repl_swift PROPERTIES
  COMPILE_FLAGS "-g0")
  endif()
  