Fwd: Error building Boost: "no best alternative for headers"

I am completely unable to build Boost libraries. I have been building on
this same computer for many years, so this issue is confounding to me. I'm
posting here in the hope that this peculiar error message might ring a bell
with someone.

After bootstrapping, when executing "b2.exe", before getting into the
actual build (which fails), these error messages are repeated multiple
times:

error: No best alternative for ./headers
>     next alternative: required properties: (empty)
>         matched
>     next alternative: required properties: (empty)
>         matched


I have attached console output from the offending build.

My actual command line is:

.\b2 -j8 toolset=msvc-14.1 --build-type=minimal --without-mpi
> --without-python address-model=32 link=shared threading=multi
> runtime-link=shared windows-api=desktop stage


Thanks in advance!

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