MinGw\bin\ar.exe: libavcodec/: Permission denied
'm not sure if this is relevant, but I had the same error when trying to make ffmpeg. Initially I was getting a missing separator error (in one of the makefiles) when I used configure. I found a page that suggested checking that git was using unix line endings rather than windows (CR LF). So I used
git config --global core.autocrlf false
to set git to use unix line endings and then thought I'd updated my source (being new to git, it turned out I hadn't). I still got the missing separator error, so I added a tab to the start of the line and configure completed. I then used make and would get the same error you're getting. I saw in some of the other makefiles that they still had windows line endings, so I deleted the entire directory apart from the .git folder as mentioned here, and then used
git reset --hard
to get the files again. After this configure and make worked without error, so my guess would be that you're using windows line endings or there's something wrong with the makefiles.
