This is on a new regression fixture, so I might be doing something wrong, but my develop regression is shunting with this at the end of bjam.log:

...
    - valgrind                 : no
warn: Unable to construct ../libs/predef/test/info_as_objcpp
warn: Unable to construct ../libs/predef/test/info_as_objc
error: at F:/boost/gcc/develop/boost_bb/src/kernel\modules.jam:107
error: Unable to find file or target named
error: '/F:/boost/gcc/develop/boost_root/status/F:/boost/gcc/develop/boost_root/libs/predef/check/predef_check_as_cpp.cpp'
error: referred to from project at
error:     '../check/predef'


The path in that one error message looks suspicious ("/F:/boost/gcc/..." duplicated).