SDL: cmake: only add -Wl,--undefined=WinMain when building an executable (c7950)

SDL Commits
1 
From c7950bf0c611981df82c0cdda7c077d6e27fd9b0 Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Tue, 27 Sep 2022 03:15:04 +0200
Subject: [PATCH] cmake: only add -Wl,--undefined=WinMain when building an
 executable

(cherry-picked from commit 653e433c08eaf48648211bca5f4148db10fa8b19)
---
 sdl2-config.cmake.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sdl2-config.cmake.in b/sdl2-config.cmake.in
index 446357fa968e..5d6cf4335f87 100644
--- a/sdl2-config.cmake.in
+++ b/sdl2-config.cmake.in
@@ -80,12 +80,12 @@ if(EXISTS "${_sdl2main_library}")
       if(CMAKE_SIZEOF_VOID_P EQUAL 4)
         set_target_properties(SDL2::SDL2main
           PROPERTIES
-            INTERFACE_LINK_OPTIONS "-Wl,--undefined=_WinMain@16"
+            INTERFACE_LINK_OPTIONS "$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:-Wl,--undefined=_WinMain@16>"
         )
       else()
         set_target_properties(SDL2::SDL2main
           PROPERTIES
-            INTERFACE_LINK_OPTIONS "-Wl,--undefined=WinMain"
+            INTERFACE_LINK_OPTIONS "$<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,EXECUTABLE>:-Wl,--undefined=WinMain>"
         )
       endif()
     endif()