CMake: default to shared library builds being enabled.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 988a348..b9694c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -216,6 +216,10 @@ if(EMSCRIPTEN)
set(SDL_DLOPEN_ENABLED_BY_DEFAULT OFF)
endif()
+if (NOT DEFINED SDL_SHARED_ENABLED_BY_DEFAULT)
+ set(SDL_SHARED_ENABLED_BY_DEFAULT ON)
+endif()
+
set(SDL_SUBSYSTEMS
Atomic Audio Video Render Events Joystick Haptic Power Threads Timers
File Loadso CPUinfo Filesystem Dlopen)