Re-apply megasource changes to SDL's cmake file

libs/SDL2/CMakeLists.txt

@@ -333,6 +333,8 @@ if(VITA)
   set(SDL_LOADSO_ENABLED_BY_DEFAULT OFF)
 endif()
 
+set(BUILD_SHARED_LIBS ON)
+
 # When defined, respect CMake's BUILD_SHARED_LIBS setting:
 set(SDL_STATIC_ENABLED_BY_DEFAULT ON)
 if (NOT DEFINED SDL_SHARED_ENABLED_BY_DEFAULT)
@@ -1518,6 +1520,8 @@ elseif(WINDOWS)
   endif()
   set(HAVE_SDL_MISC TRUE)
 
+  set(SDL_LINK_DIR ${PARENT_SCOPE})
+
   # Check for DirectX
   if(SDL_DIRECTX)
     if(DEFINED MSVC_VERSION AND NOT ${MSVC_VERSION} LESS 1700)
@@ -1550,6 +1554,8 @@ elseif(WINDOWS)
     set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
   endif()
 
+  link_directories(${SDL_LINK_DIR})
+
   if(SDL_XINPUT)
     # xinput.h may need windows.h, but does not include it itself.
     check_c_source_compiles("
@@ -2766,6 +2772,13 @@ if(SDL_STATIC)
   endif()
 endif()
 
+if(MEGA)
+  if(SDL_SHARED)
+    install(TARGETS SDL2 RUNTIME DESTINATION . LIBRARY DESTINATION .)
+  endif()
+  return()
+endif()
+
 ##### Tests #####
 
 if(SDL_TEST)