Gentoo's Bugzilla –
Attachment 659874 Details for
Bug 741969media-sound/audacity-2.4.2-r1[-flac] - ld: src/CMakeFiles/Audacity.dir/ondemand/ODDecodeFlacTask.cpp.o: in function `ODFlacDecoder::ReadHeader()': ODDecodeFlacTask.cpp:(.text+0x768): undefined reference to `FLAC::Decoder::File::File()'