gcc: Force linking to libgcc_s_dw2-1.dll

.. by adding to specs:
*libgcc
--undefined=___deregister_frame_info
--undefined=___register_frame_info

These flags get added twice to the ld command line
 because of %G appearing twice in:
*link_gcc_c_sequence
%G %L %G
so this should be tidied up really.
gcc: Fix new patch, bump pkgrel