[boost] [date_time] [build] new windows class of build error?

Subject: [boost] [date_time] [build] new windows class of build error?
From: James E. King, III (jking_at_[hidden])
Date: 2018-01-12 18:49:09

I enabled appveyor for Boost.DateTime pull requests and they are failing
miserably when <cxxstd> is specified more than once.  I don't remember this
occurring in the past.  This happens on Visual Studio, cygwin, mingw
builds.  Is this new Boost.Build behavior?

https://ci.appveyor.com/project/jeking3/date-time-1evbf/build/1.0.3-develop

error: Name clash for '<pstage\lib>libboost_atomic-vc140-mt-x32-1_67.lib'
error: error: Tried to build the target twice, with property sets having
error: these incompatible properties: error: error: - <cxxstd>14 error: -
<cxxstd>17 error: error: Please make sure to have consistent requirements
for these error: properties everywhere in your project, especially for
install error: targets. Command exited with code 1