-ggdb3 make slightly bigger .elf files, but allows gdb to understand
macros, which libopenocm3 uses somewhat extensively. Make this the
default, and pull it up to the common base makefile, so it can be easily
substituted.
On linux, the output of CP rule was try to write to / which is - of course, forbidden for write.
This solution adds to each part of lib correct pointer to the root of lib where the libs should be written.
Bug found by Kuldeep Singh Dhaka.
