[Buildroot] [PATCH v2] gst1-av: fix cpu detection in libav configure

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Arnout" == Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> writes:

 > The configure script tries to guess a lot based on the cpu for which it
 > is configured. Without --cpu, it will use a 'generic' cpu and disable
 > any other options we pass to it.

 > In addition, we have to pass the --sysroot option like we do in the
 > ffmpeg package. This makes sure that regardless of the architecture
 > options that ffmpeg passes along, an external multilib toolchain
 > doesn't try to use a subdirectory of the sysroot. The libav build
 > system will pass a --isysroot argument which overrides the multilib
 > subdir.

 > Finally, we have to properly enable/disable the architecture-specific
 > optimisations. Autodetection of these things is completely borked in
 > the configure script.

 > Fixes:
 > http://autobuild.buildroot.net/results/ce83513135e7765c171353815947d715eb897d3d

 > Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
 > Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
 > ---
 > v2: improve commit message

 > The --isysroot is something we should probably do in the toolchain
 > wrapper.

What is the advantage of --isysroot over --sysroot? I don't seem to find
a lot about in the gcc documentation, but it seems like:

- isysroot only applied to headers, not headers+libraries like --sysroot
- Some versions of MacOSX/llvm only support --isysroot, not --sysroot

Neither of these seems of much interest to us?

-- 
Bye, Peter Korsgaard