fix __builtin___clear_cache overrider fallout

fix __builtin___clear_cache overrider fallout

Machines that had CLEAR_CACHE_INSN and that would thus issue calls to
__clear_cache with the default call expander, would fail on languages
that did not set up the __clear_cache builtin.  This patch arranges
for all languages to set up this builtin.

Machines or multilibs that had ptr_mode != Pmode, such as aarch64 with
-mabi=ilp32, would fail the RTL mode test of the arguments passed to
__clear_cache, because we'd insist on ptr_mode.  This patch arranges
for Pmode to be accepted as well.

for  gcc/ChangeLog

	* tree.c (build_common_builtin_nodes): Declare
	__builtin___clear_cache for all languages.
	* builtins.c (maybe_emit_call_builtin___clear_cache): Accept
	Pmode arguments.