Use ghc return value instead of looking for the stderr, do not throw error when an haskell module throws a build failure, e.g. because of false positives like this one (debian/arm*) "You are using a new version of LLVM that hasn't been tested yet! We will try though..."

/* Generated by ffconf */
#ifndef AVUTIL_AVCONFIG_H
#define AVUTIL_AVCONFIG_H
#define AV_HAVE_BIGENDIAN 0
#define AV_HAVE_FAST_UNALIGNED 1
#endif /* AVUTIL_AVCONFIG_H */