SDL_mixer: cmake: Turn off PLATFORM_SUPPORTS_SHARED by default for MS-DOS.

SDL Commits
1 
From 6ef3335eee60479a986a508f5dd59e433d1184da Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 2 Jun 2026 13:23:40 -0400
Subject: [PATCH] cmake: Turn off PLATFORM_SUPPORTS_SHARED by default for
 MS-DOS.

(We can turn this back on for DXEs eventually.)
---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 962bd258..95502300 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -92,7 +92,7 @@ include(GNUInstallDirs)
 include(PkgConfigHelper)
 
 set(PLATFORM_SUPPORTS_SHARED ON)
-if(EMSCRIPTEN OR VITA OR PSP OR PS2 OR N3DS OR RISCOS)
+if(EMSCRIPTEN OR VITA OR PSP OR PS2 OR N3DS OR RISCOS OR DOS)
   set(PLATFORM_SUPPORTS_SHARED OFF)
 endif()