[Boost-build] What is the most proper way to use installed boost library in couple with boost.build?

Subject: [Boost-build] What is the most proper way to use installed boost library in couple with boost.build?
From: Dmitry Timoshenko (dimentiy2k_at_[hidden])
Date: 2011-07-04 14:25:57

Hello,

I have a project used boost libraries and linked against them.
I also use boost.build to build the project.

If boost libraries are used as is. With no installation (./bjam install).
I mean a user just unpack boost_1_xx.zip and specify the path
to unpacked content via e.g. BOOST_ROOT environment variable.
BOOST_ROOT points to the boost's Jamroot file location.
In this case everything is fine.
I just write the line is my project-config.jam

use-project boost : $(BOOST_ROOT) ;

and can use libraries by theirs names.

for example: boost/filesystem//boost_filesystem

and boost.build will do all the stuff for me (build dependencies and etc.).

But what if user installed boost libraries to e.g. by default 
'/usr/local' or 'c:\boost' what is common and most right way to use the 
boost in couple with boost.build in my project?

Should I declare all the prebuilt targets explicitly in this case?
The boost could also be built with different --layout specified.
How to use installed boost libraries without boost's Jamroot file?

Thank you.