Add linking to bz2 on compilation step

[dmelo]

Without linking, the following error happens:

/usr/bin/ld: ./libav/libavformat/libavformat.a(matroskadec.o): in function `matroska_decode_buffer':
/home/dmelo/proj3/untrunc/libav/libavformat/matroskadec.c:1163: undefined reference to `BZ2_bzDecompressInit'
/usr/bin/ld: /home/dmelo/proj3/untrunc/libav/libavformat/matroskadec.c:1177: undefined reference to `BZ2_bzDecompress'
/usr/bin/ld: /home/dmelo/proj3/untrunc/libav/libavformat/matroskadec.c:1171: undefined reference to `BZ2_bzDecompressEnd'
/usr/bin/ld: /home/dmelo/proj3/untrunc/libav/libavformat/matroskadec.c:1180: undefined reference to `BZ2_bzDecompressEnd'

Running on Fedora 35:

❯ uname -a
Linux solomon 5.19.16-100.fc35.x86_64 #1 SMP PREEMPT_DYNAMIC Sun Oct 16 21:50:15 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux