glibc: map hwcap=avx2 to a libdir of its own

haswell is mapped like this:
(libc6,x86-64, hwcap: 0x0004000000000000) => /usr/lib/x86_64-linux-gnu/haswell

… but as that implies popcnt and rdrand, albeit both are not as important as is avx and avx2 and libraries for the libdir could be compiled without, I'd like to have avx2 its own libdir with libraries optimized for znver1 such as the AMD Epyc 7281 (note: has those instruction sets—do all znver1 fit into haswell?).

Images published in Q1'2019 come with optimizations for Haswell and Skylake (avx512_1), starting with encoders. Benchmarks indicate it's worthwhile to spend bytes here, but as compiling is actually faster on AMDs optimizations for it will likely be needed in late 2019.

mark-kubacki / apt-image

glibc: map hwcap=avx2 to a libdir of its own #20