Fix mbed build on Windows machines with Cygwin

I had fixed this awhile ago in the core gcc4mbed makefiles but it
somehow got missed in the makefile used specifically for building the
mbed SDK library in Smoothie.  This fix makes sure that GNU make uses
the Windows Command Prompt instead of the Cygwin bash shell.  Without
this change, you could see errors like:
    /usr/bin/sh: copy: command not found
when building on a Windows machine.
Make PID work like arduino pid library and more like Marlin
Fix Clear watch screen on glcd
Allow auto pid to use full power
Merge pull request #219 from wolfmanjm/fix/pid2

Fix/pid2
Merge remote-tracking branch 'upstream/edge' into working
add example pid control settings
add example pid control settings
Merge pull request #221 from wolfmanjm/upstreamedge

Upstreamedge
Merge remote-tracking branch 'upstream/edge' into working
reset dfu-util after flashing
added flash bootloader tools