drop __builtin_ from __clear_cache libname

drop __builtin_ from __clear_cache libname

I made a cut&pasto in my previous patch for tree.c, causing platforms
that have CLEAR_INSN_CACHE defined, and none of the internal
__clear_cache expansion overriders, to issue calls to symbols named
__builtin___clear_cache rather than __clear_cache, on languages other
than those in the C family.  Oops.

This patch removes __builtin_ from the string used as the libname for
__buuiltin___clear_cache.

for  gcc/ChangeLog

	* tree.c (build_common_builtin_nodes): Drop __builtin_ from
	__clear_cache libname.