By default, converted figures (m_k_i_v_foo.pdf for source figure foo.svg) are written to the same directory as the source figure. I would like all converted figures to be written instead to a cache directory in my home directory. How do I set this path?

I asked this question on the ConTeXt users mailing list, but no one had an answer. Is there no user interface (environment variable, command line parameter, etc.) available to change where converted figures are written on disk?