Make clean extensible

[cletomartin]

Hi,

sorry if this is was already discussed but I haven't seen it in the issue list. Please, point me to the concrete issue if exists.

Could you please change the target definition of clean to:

clean::

Using two-colon notation let the user to extend the actions during cleaning. E.g:

include /usr/share/arduino/Arduino.mk

clean::
    $(RM)  *~

Thus, apart from removing build directory, it also deletes all my backup files.

Cheers!

[sej7278]

that's a good idea actually, something i already work around in my makefiles, but this is a better way to do it. fixed in PR #240

[sudar]

Thanks @cletomartin for reporting it and @sej7278 for implementing it.