build failure, gcc4 merged over Binutils 2.15.97

[DJ Delorie]

> Merging the other way (gcc over binutils) broke. Specifically,
> include/libiberty.h in binutils contains
> 
> 	extern int unlink_if_ordinary PARAMS((const char *));

We try very hard to keep libiberty backward compatible.  It's nearly
impossible to keep it *forward* compatible.  You should always be able
to replace a libiberty with a newer version, but you can't always
replace it with an older one.

Note that "libiberty" is more than just the libiberty subdirectory;
portions of the include directory are part of libiberty also.

So, just figure out which libiberty is newer, and use that one.