configure: add pkg-config support for libx264

Reviewed-by: Carl Eugen Hoyos <cehoyos@ag.or.at>
Tested-by: Carl Eugen Hoyos <cehoyos@ag.or.at>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -4880,7 +4880,10 @@ enabled libvpx            && {
     enabled libvpx_vp9_encoder && { check_lib2 "vpx/vpx_encoder.h vpx/vp8cx.h" "vpx_codec_vp9_cx VP9E_SET_AQ_MODE" -lvpx || disable libvpx_vp9_encoder; } }
 enabled libwavpack        && require libwavpack wavpack/wavpack.h WavpackOpenFileOutput  -lwavpack
 enabled libwebp           && require_pkg_config "libwebp >= 0.2.0" webp/encode.h WebPGetEncoderVersion
-enabled libx264           && require libx264 x264.h x264_encoder_encode -lx264 &&
+enabled libx264           && { { check_pkg_config x264 "stdint.h x264.h" x264_encoder_encode &&
+                                 require_pkg_config x264 "stdint.h x264.h" x264_encoder_encode; } ||
+                               { require libx264 x264.h x264_encoder_encode -lx264 &&
+                                 warn "using libx264 without pkg-config"; } } &&
                              { check_cpp_condition x264.h "X264_BUILD >= 118" ||
                                die "ERROR: libx264 must be installed and version must be >= 0.118."; }
 enabled libx265           && require_pkg_config x265 x265.h x265_encoder_encode &&