set workdir to the shared folder

Author: leandromoreira

Makefile

@@ -2,10 +2,10 @@ clean:
 	@rm -rf ./build/*
 
 make_hello: clean
-	docker run --rm -it -v `pwd`:/files leandromoreira/ffmpeg-devel \
+	docker run -w /files --rm -it  -v `pwd`:/files leandromoreira/ffmpeg-devel \
 	  gcc -L/opt/ffmpeg/lib -I/opt/ffmpeg/include/ /files/0_hello_world.c \
 	  -lavcodec -lavformat -lavfilter -lavdevice -lswresample -lswscale -lavutil \
 	  -o /files/build/hello
 
 run_hello: make_hello
-	docker run --rm -it -v `pwd`:/files leandromoreira/ffmpeg-devel /files/build/hello /files/small_bunny_1080p_60fps.mp4
+	docker run -w /files --rm -it -v `pwd`:/files leandromoreira/ffmpeg-devel /files/build/hello /files/small_bunny_1080p_60fps.mp4