This got me further, but it ultimately still failed later in the config with a similar error:
...
- std_wstreambuf builds : yes [2]
- std_wstreambuf : yes [2]
- BOOST_COMP_GNUC >= 4.3.0 : no [2]
- BOOST_COMP_GNUC >= 4.3.0 : no [3]
error: Unable to find file or target named
error: 'libs/thread/build//boost_MYextralLabel_thread'
error: referred to from project at
error: '.'
Notable differences in this error message are that now the target it's unable to find contains my custom namespace, and now the project referring to it is '.' instead of a path to subdirectory.
Also notable that this new error is the same error I previously received if I deleted the 'boost' output directory after running `bcp` but before running `bootstrap`. So it seems that your suggested past gets past one bug but reveals the next bug.
Thanks,
Nick