src.conf option WITHOUT_LZMA_SUPPORT has no effect. The library and the xz utilities are always built. There is no use of MK_LZMA_SUPPORT throught the whole base system.
I have added support for MK_LZMA_SUPPORT in gzip(1), and on amd64 -CURRENT, the version without LZMA support is only 8KiB smaller than the version with it. The shared object itself is about 180KiB.
I think if the goal is to support it, we should teach build system about it (e.g. don't build LZMA libraries, etc.), but personally I don't see much point of doing this so perhaps we should just remove this option.
-> imp@ for triage.
The option was added in r263997 and the sole user was grep. Compression support was removed in r332995 by bapt@.