Compile Hang on Marlin

1.6.4 / XP

verbose logging shows an attempt to access … .tmp/core.a -LC … .tmp -lm
and it hangs there.
Now, the FORWARD slash doesn’t look right in the context of all the BACKSLASHES, given
that it’s windows, not *ux.

THis line follows …liwquidcrystal.cpp.0 and spi.cpp.o info which seems to have loaded ok.

Is the / normal, or is there a fix or workaround? /thanks!