libphobos: Fix multilib powerpc64 builds

libphobos: Fix multilib powerpc64 builds

Multilibs should not have been split up as two logically different CPU,
so at configure time, powerpc64 was being detected, but none of the
32-bit support files were being compiled in.

libphobos/ChangeLog:

	PR d/94825
	* configure: Regenerate.
	* libdruntime/Makefile.am (DRUNTIME_SOURCES_CONFIGURED): Add both
	switchcontext.S and callwithstack.S if DRUNTIME_CPU_POWERPC.
	* libdruntime/Makefile.in: Regenerate.
	* libdruntime/config/powerpc/switchcontext.S: Add !__PPC64__ guards.
	* libdruntime/config/powerpc64/callwithstack.S: Add __PPC64__ guards.
	* m4/druntime/cpu.m4 (DRUNTIME_CPU_SOURCES): Define DRUNTIME_CPU_POWER
	for all powerpc biarchs.  Remove DRUNTIME_CPU_POWER64 conditional.