follow the instruction of the tutorial, when making toolchain, some errors came out for SDL.

cc1: warning: include location "/usr/include" is unsafe for cross-compilation
cc1: warning: include location "/usr/include/directfb" is unsafe for cross-compilation
./src/audio/dma/SDL_dmaaudio.c: In function 'DMA_WaitAudio':
./src/audio/dma/SDL_dmaaudio.c:166: error: impossible constraint in 'asm'
make[2]: *** [build/SDL_dmaaudio.lo] Error 1
make[2]: Leaving directory `/srv/preware/build/toolchain/libsdl/build/src'
make[1]: *** [build/armv7.built-1.2-1] Error 2
make[1]: Leaving directory `/srv/preware/build/toolchain/libsdl'
make: *** [staging/usr/include/SDL/SDL.h] Error 2

the tutorial link here: Building Apps and Kernels - WebOS Internals


it seems that the include is unsafe. So how can i do?