[Cin] Internal engine and ffmpeg

[Andrea paz]

I continue here what we started in MantiBT #646 since my problems are
not with the issue.
I tried making a build that uses system ffmpeg instead of CinGG's
internal one. The behavior is the usual, even though the internal
engine for exr is active, ffmpeg is used. The result is the same:
clipped exr images except one.
Maybe I am doing something wrong in the copy/paste I do during
compilation? I report the exact steps (not from root):

git clone --depth 1 "git://git.cinelerra-gg.org/goodguy/cinelerra.git"
cinelerra5
cd /home/paz/cinelerra5/cinelerra-5.1
[patching here]
./autogen.sh
./configure --with-single-user --with-config-dir=/home/paz/.bcast6
--with-booby  ### .bcast5 is for appimage
make 2>&1 | tee /tmp/cin5.log && make install
mv Makefile Makefile.cfg
cp Makefile.devel Makefile

(Curiosity: what are the last 2 steps for?)
Do you guys have any improvements to propose to this set of steps?

If these steps are correct then I can only think that it is Arch,
although I don't see how...