configure: (vp9) ensure bitstream compatibility

avoids picking up a library that could produce invalid bitstreams and
fixes build issues with the same.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -4427,7 +4427,7 @@ enabled libvpx            && {
     enabled libvpx_vp8_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_enc_init_ver VP8E_SET_MAX_INTRA_BITRATE_PCT" -lvpx ||
                                     die "ERROR: libvpx encoder version must be >=0.9.7"; }
     enabled libvpx_vp9_decoder && { check_lib2 "vpx/vpx_decoder.h vpx/vp8dx.h" "vpx_codec_vp9_dx" -lvpx || disable libvpx_vp9_decoder; }
-    enabled libvpx_vp9_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_vp9_cx" -lvpx || disable libvpx_vp9_encoder; } }
+    enabled libvpx_vp9_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_vp9_cx VP9E_SET_SVC" -lvpx || disable libvpx_vp9_encoder; } }
 enabled libwavpack        && require libwavpack wavpack/wavpack.h WavpackOpenFileOutput  -lwavpack
 enabled libx264           && require libx264 x264.h x264_encoder_encode -lx264 &&
                              { check_cpp_condition x264.h "X264_BUILD >= 118" ||