On Fri, Oct 23, 2020 at 2:12 PM Ryan Heniser via Boost-users <boost-users@lists.boost.org> wrote:

Hi,

I am building Boost 1.61 (we need this old version for other libraries) for the first time at work with Boost.Build (b2). I have successfully built Boost (using b2) for gcc 4.8. If I want to add one or more variants (for example using gcc 6.3), where should I put the Boost header’s include directory?

So the header directory  isn't going to change since it's the same version of boost, but the output directories will.  First you'll need to add another variant to your user-config.jam file.  Like this

using gcc : 6.3 : g++-6.3 ;

where g++-6.3 is the compiler ext name. Then when you invoke b2 you'll name the toolset:

b2 -toolset=gcc-6.3

in the bin.v2 subdirectories you'll see new subtrees for the newly compiled variants.
 libs/date_time/build/gcc-4.8/release/...
 libs/date_time/build/gcc-6.3/release/... 

Should one go inside each variant or should just one go at the root directory containing the variant directories?

Not sure I understand the question...