user/ffmpeg: (ppc) ld: libavformat/libavformat.so: undefined reference to `__atomic_*_8'
Found on 32-bit ppc. Not exactly sure what is the root cause, but documenting here anyway.
LD ffplay_g
LD ffprobe_g
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_sub_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_load_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_add_8'
collect2: error: ld returned 1 exit status
make: *** [Makefile:124: ffplay_g] Error 1
make: *** Waiting for unfinished jobs....
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_sub_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_load_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_add_8'
collect2: error: ld returned 1 exit status
make: *** [Makefile:124: ffprobe_g] Error 1
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_sub_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_load_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_store_8'
/usr/lib/gcc/powerpc-foxkit-linux-musl/8.3.0/../../../../powerpc-foxkit-linux-musl/bin/ld: libavformat/libavformat.so: undefined reference to `__atomic_fetch_add_8'
collect2: error: ld returned 1 exit status
make: *** [Makefile:124: ffmpeg_g] Error 1
>>> ERROR: ffmpeg: build failed