I am trying to implement conditional includes
of sources/lib's depending on the tool set i.e
Take the following jamfile snippet

....
# common libs
lib pthread ;

# On HPUX we need to add standard libs.
lib std_v2 ;
lib stream ;
lib Csup ;
lib unwind ;
lib m ;

alias std_libs : pthread : <toolset>gcc ;
alias std_libs : pthread : <toolset>vacpp ;
alias std_libs : pthread std_v2 stream Csup unwind m :   <toolset>acc ;

python-extension ecf_ext : [ glob src/*.cpp ]
             /theCore//core
             /site-config//boost_system
             /site-config//boost_thread
             /site-config//boost_serialization
             /site-config//boost_filesystem
             /site-config//boost_program_options
             /site-config//boost_datetime
             std_libs
           : <variant>debug:<define>DEBUG
           ;

I am using alias std_libs to conditionally add additional libs on HPUX.

My site-config.jam on AIX look like:
......
project site-config
        : requirements <include>$(BOOST_ROOT)
        : requirements <threading>multi
        ;
using vacpp ;
using testing ;

Originally when I tested this on Linux, it worked a charm. However on
AIX and HPUX, I get messages like:

error: No best alternative for ./std_libs
    next alternative: required properties: <threading>multi <toolset>gcc
        not matched
    next alternative: required properties: <threading>multi <toolset>vacpp
        not matched
    next alternative: required properties: <threading>multi <toolset>acc
        not matched
...patience...

I don't understand why it cant make the correct choice, as it has all
the information, i.e for toolset and threading ?

Is there any better way of achieving conditional source/libs
dependent on toolset, apart from specifying on the command line ?

Any help on this matter appreciated.

Best regards,
Ta,
Avi