In /vlc/modules/video_filter/deinterlace/algo_x.c
Find the lines (around line 500 or so):
#ifdef CAN_COMPILE_MMXEXT
VLC_MMX
static inline void XDeintBand8x8MMXEXT( uint8_t *dst, int i_dst,
uint8_t *src, int i_src,
const int i_mbx, int i_modx )
and remove the line 'VLC_MMX'
Vlc now builds, and as far as I can tell seems to work fine...