Select provider of libav* libraries

[Andreas Cadhalpun]

Hi Fabian,

On 08.06.2015 11:18, Fabian Greffrath wrote:
> Am Sonntag, den 07.06.2015, 20:45 +0200 schrieb Andreas Cadhalpun:
>> It seems it doesn't really work, because calling configure again 
>> causes make to rebuild everything.

Actually only if one changes the configure arguments things get rebuild
and only those including config.h.

> That's somehow stupid, isn't it?

Not really, because a large part of the code can be influenced with
configure options.
But if one just enables additional codecs, rebuilding is not really
necessary (only libavcodec/allcodecs.o has to be rebuilt then.)

So one can just use two directories, first run configure in both (with
the different options), then compile the GPLv2 variant, copy the
object files (without allcodecs.o) to the GPLv3 folder, build the
remaining GPLv3 de-/encoders there and link the libraries again.

Best regards,
Andreas