Don't add extra build linker flags to SDL2_static

These leak to users, when SDL2 is vendored.

CMakeLists.txt

@@ -3013,7 +3013,7 @@ if(SDL_STATIC)
   endif()
   # TODO: Win32 platforms keep the same suffix .lib for import and static
   # libraries - do we need to consider this?
-  target_link_libraries(SDL2-static PRIVATE ${EXTRA_LIBS} ${EXTRA_LDFLAGS} ${EXTRA_LDFLAGS_BUILD})
+  target_link_libraries(SDL2-static PRIVATE ${EXTRA_LIBS} ${EXTRA_LDFLAGS})
   target_include_directories(SDL2-static BEFORE PRIVATE "${SDL2_BINARY_DIR}/include")
   target_include_directories(SDL2-static PUBLIC "$<BUILD_INTERFACE:${SDL2_SOURCE_DIR}/include>" $<INSTALL_INTERFACE:include> $<INSTALL_INTERFACE:include/SDL2>)
   # This picks up all the compiler options and such we've accumulated up to here.