[ffmpeg] Add --ffmpeg-location

youtube_dl/options.py

@@ -735,6 +735,10 @@ def parseOpts(overrideArguments=None):
         '--prefer-ffmpeg',
         action='store_true', dest='prefer_ffmpeg',
         help='Prefer ffmpeg over avconv for running the postprocessors')
+    postproc.add_option(
+        '--ffmpeg-location', '--avconv-location', metavar='PATH',
+        dest='ffmpeg_location',
+        help='Location of the ffmpeg/avconv binary; either the path to the binary or its containing directory.')
     postproc.add_option(
         '--exec',
         metavar='CMD', dest='exec_cmd',