Re-apply megasource-specific changes to SDL's CMakeLists.

- Enable SDL_SHARED and disable SDL_STATIC.

- Set SDL_LINK_DIR in parent scope.

- Use custom install() directive.

- Add target_include_directories.

libs/SDL2/CMakeLists.txt

@@ -336,8 +336,8 @@ dep_option(KMSDRM_SHARED       "Dynamically load KMS DRM support" ON "VIDEO_KMSD
 
 # TODO: We should (should we?) respect cmake's ${BUILD_SHARED_LIBS} flag here
 # The options below are for compatibility to configure's default behaviour.
-set(SDL_SHARED ${SDL_SHARED_ENABLED_BY_DEFAULT} CACHE BOOL "Build a shared version of the library")
-set(SDL_STATIC ON CACHE BOOL "Build a static version of the library")
+set(SDL_SHARED ON CACHE BOOL "Build a shared version of the library")
+set(SDL_STATIC OFF CACHE BOOL "Build a static version of the library")
 
 dep_option(SDL_STATIC_PIC      "Static version of the library should be built with Position Independent Code" OFF "SDL_STATIC" OFF)
 
@@ -1140,6 +1140,8 @@ elseif(WINDOWS)
     endif()
   endif()
 
+  set(SDL_LINK_DIR ${PARENT_SCOPE})
+
   # Check for DirectX
   if(DIRECTX)
     if(DEFINED MSVC_VERSION AND NOT ${MSVC_VERSION} LESS 1700)
@@ -1185,13 +1187,15 @@ elseif(WINDOWS)
       set(HAVE_DIRECTX TRUE)
       if(NOT CMAKE_COMPILER_IS_MINGW AND NOT USE_WINSDK_DIRECTX)
       # TODO: change $ENV{DXSDL_DIR} to get the path from the include checks
-        link_directories($ENV{DXSDK_DIR}\\lib\\${PROCESSOR_ARCH})
+        set(SDL_LINK_DIR $ENV{DXSDK_DIR}\\lib\\${PROCESSOR_ARCH} ${SDL_LINK_DIR})
         include_directories($ENV{DXSDK_DIR}\\Include)
       endif()
     endif()
     set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
   endif()
 
+  link_directories(${SDL_LINK_DIR})
+
   if(SDL_AUDIO)
     set(SDL_AUDIO_DRIVER_WINMM 1)
     file(GLOB WINMM_AUDIO_SOURCES ${SDL2_SOURCE_DIR}/src/audio/winmm/*.c)
@@ -1694,6 +1698,7 @@ set(_INSTALL_LIBS "SDL2main")
 
 if(SDL_SHARED)
   add_library(SDL2 SHARED ${SOURCE_FILES} ${VERSION_SOURCES})
+  install(TARGETS SDL2 RUNTIME DESTINATION . LIBRARY DESTINATION .)
   if(APPLE)
     set_target_properties(SDL2 PROPERTIES MACOSX_RPATH 1)
   elseif(UNIX AND NOT ANDROID)
@@ -1715,7 +1720,7 @@ if(SDL_SHARED)
   endif()
   set(_INSTALL_LIBS "SDL2" ${_INSTALL_LIBS})
   target_link_libraries(SDL2 ${EXTRA_LIBS} ${EXTRA_LDFLAGS})
-  target_include_directories(SDL2 PUBLIC $<INSTALL_INTERFACE:include>)
+  target_include_directories(SDL2 PUBLIC include)
 endif()
 
 if(SDL_STATIC)
@@ -1742,6 +1747,11 @@ if(SDL_STATIC)
 endif()
 
 ##### Installation targets #####
+
+if(MEGA)
+  return()
+endif()
+
 install(TARGETS ${_INSTALL_LIBS} EXPORT SDL2Targets
   LIBRARY DESTINATION "lib${LIB_SUFFIX}"
   ARCHIVE DESTINATION "lib${LIB_SUFFIX}"