[PATCH] Allow parallel toplevel bootstrap

[Richard Earnshaw]

This patch breaks building with a unified build tree.  We now get:

arm-elf-ar  rc ./libgcc.a libgcc/./_udivsi3.o libgcc/./_divsi3.o
libgcc/./_umodsi3.o libgcc/./_modsi3.o libgcc/./_dvmd_tls.o [...]
libgcc/./gthr-gnat.o libgcc/./unwind-c.o
gnumake[3]: arm-elf-ar: Command not found
gnumake[3]: *** [libgcc.a] Error 127

The problem is in the top-level makefile with the extra level of
recursion that is now used.

AR_FOR_TARGET in this case is intended to expand to ..../binutils/ar,
but the macro to do this is in RECURSE_FLAGS_TO_PASS, and that's
expanded before we've built binutils, so instead of pointing to the
newly created ar it points to the non-existant arm-elf-ar.

Restarting the make after binutils has been built should work ok, but
that's not really the point.

R.