[boost] setting <cxxflags> and <linkflags> in Jamfile?

Hello, if the define BOOST_USE_XYZ is given at b2/bjam command-line how can I set special compiler- and linker-flags in the Jamfile? something like this: Jamfile.v2: *project boost/abc : requirements <toolset>gcc-4.7,<defined>BOOST_USE_XYZ:<cxxflags>-fxyz <toolset>gcc-4.7,<defined>BOOST_USE_XYZ:<linkflags>"-static-libxyz" <link>static <threading>multi : source-location ../src : usage-requirements <link>shared:<define>BOOST_ABC_DYN_LINK=1 ; * if the lib is build with b2 toolset=gcc cxxflags="-DBOOST_USE_XYZ" then -fxyz static-libxyz is applied to the compiler otherwise not. How can I achieve this behaviour? best, Oliver