[Boost-users] [log] Possible to explicitly disable AVX2?

I am building Boost.Log on a relatively new machine whose compiler and CPU both support the AVX2 instruction set. Boost.Log detects this at build time and configures its compiler flags accordingly to use the AVX2 instruction set. I'd like to use the resulting binaries, however, on older systems that do not have AVX2 support. Is it possible to explicitly disable this at build time? I didn't see any mention of it in the documentation, and my attempts to parse the Jamfile's intentions were not successful. Thank you. Jason