Pull up following revision(s) (requested by msaitoh in ticket #612):
external/gpl3/gcc/lib/libgcc/Makefile.inc: revision 1.15
Don't add unwind.h stuff into BUILDSYMLINKS when MKGCC=="no".
Fixes "Wrong number of words (1) in .for substitution list with 2 vars" problem
while mknative-ing. Approved by mrg.