cc-rs allows users to override the compiler used for a specific target triple by setting the environment variable CC_<triple>, but for targets such as thumv8m.main-none-eabi this doesn't work as .-s are not allowed to be used in the name of an environment variable in (most?) shells, so setting e.g. CC_thumbv8m.main_none_eabi is not allowed.

It would be great if this could be supported, either by replacing the . with an _, or some other solution that allows us to actually set this environment variable.