[boost] [build] Algorithm for setting PATH when a 'run' or 'run-fail'

What is the algorithm for setting a PATH on Windows when the 'run' or 'run-fail' rule occurs in a jamfile ? In running clang on Windows when an executable is created the PATH needs to start with the bin directory of the mingw(-64)/gcc implementation that a particular version of clang uses as its RTL when the program is compiled/linked. It appears that when the 'run' or 'run-test' rule occurs with the clang toolset on Windows that the PATH is adjusted to have the directory of the clang++ executable and not that of the corresponding mingw(-64)/gcc RTL ? Is there any solution to this from within Boost Build ?