boost root include folder

From: Alexander Grund (alexander.grund_at_[hidden])
Date: 2021-04-12 06:50:32

Hi all,

I wanted to propose moving the top-level include folder "boost" 
(basically a symlink to all libs/*/include/boost headers) into a 
subfolder "include" and add (only) that to `-I` by the root Jamfile. See 
https://github.com/boostorg/boost/issues/501

In short: The current practice of adding the project root folder to the 
include paths leads to compilers picking up non-header files, like 
<version>, which has led to trouble in other projects already. (Not a 
problem with Boost yet AFAIK, so this is a general observation)

Boost should be a good example, and NOT do that too.

There might be some fallout outside of Boost for users not using an 
installed or staged Boost version but rely on the root boost folder, but 
the fix is trivial and IMO well reasoned. And e.g. CMake (very likely) 
would already handle that change just fine without modifications.

Regards,
Alex