Modify default link flag "subsystem"

Code
4

Hmm, here’s what I have in my project and that works fine (unless I misunderstood what you wanted to achieve in yours):

set_target_properties(HERE-IS-MY-EXECUTABLE-TARGET-NAME
    PROPERTIES
    LINK_FLAGS "/ENTRY:mainCRTStartup /SUBSYSTEM:WINDOWS"
)

Looking at your code, one difference is that my flags are quoted and another difference is that they are in upper case (your /subsystem is lower-cased). Not sure if any of these differences matter, though.

Also it could be that you have a typo in your target name? But that would have caused a different kind of problem, unless you have another target with that name.