Added Intel Media SDK plugins path for hw-accelerated QSV encoders

This seems to not work currently with the Intel binary version of
Media SDK. But the correct is to provide this path for ffmpeg to
try the hardware accelerated encoders before falling back to
software mode. Only software mode seems to be working currently,
and then intel-media-sdk optdepend will still remain marked as
experimental.

PKGBUILD

@@ -4,7 +4,7 @@
 pkgname=ffmpeg-full
 _srcname=ffmpeg
 pkgver=3.3.3
-pkgrel=3
+pkgrel=4
 pkgdesc='Record, convert and stream audio and video (all possible features including nvenc, qsv and libfdk-aac)'
 arch=('i686' 'x86_64')
 url='http://www.ffmpeg.org/'
@@ -68,7 +68,7 @@ build() {
         _cuvid='--enable-cuvid'
         _libnpp='--enable-libnpp'
         _cflags='--extra-cflags=-I/opt/cuda/include'
-        _ldflags='--extra-ldflags=-L/opt/cuda/lib64 -Wl,-rpath -Wl,/opt/intel/mediasdk/lib64'
+        _ldflags='--extra-ldflags=-L/opt/cuda/lib64 -Wl,-rpath -Wl,/opt/intel/mediasdk/lib64:/opt/intel/mediasdk/plugins'
     fi
     
     msg2 'Running ffmpeg configure script. Please wait...'