meta-firefox: Adding python to HOSTTOOLS is causing issues with systemtap (maybe others)

[FederAndInk]

Just a note that adding python to HOSTTOOLS is causing systemtap to fail to configure as it will be looking for ${python3_basename}-config which will expend to python-config instead of python3-config, I guess this could be solved in multiple ways (adding python-config link to python3-config, patching systemtap configure, ...)

It's just a note, as it was not trivial to debug and might impact other recipes.