This might depend on the version of jam you are using. Speaking for the standard jam (i.e. not the Boost or FreeType forks): There is no official way, but you might get away with:
jam -sJAMFILE=path/to/Jamfile ...
For more complex build systems that also have a configure stage, I'd recommend to simply generate a minimal Jamfile in those output directory/directories from which you intend to invoke jam.
This might depend on the version of jam you are using. Speaking for the standard jam (i.e. not the Boost or FreeType forks): There is no official way, but you might get away with:
For more complex build systems that also have a configure stage, I'd recommend to simply generate a minimal Jamfile in those output directory/directories from which you intend to invoke jam.