libgcc: Fix up i386/t-heap-trampoline [PR113403]

I'm seeing
../../../libgcc/shared-object.mk:14: warning: overriding recipe for target 'heap-trampoline.o'
../../../libgcc/shared-object.mk:14: warning: ignoring old recipe for target 'heap-trampoline.o'
../../../libgcc/shared-object.mk:17: warning: overriding recipe for target 'heap-trampoline_s.o'
../../../libgcc/shared-object.mk:17: warning: ignoring old recipe for target 'heap-trampoline_s.o'

This patch fixes that.

2024-02-01  Jakub Jelinek  <jakub@redhat.com>

	PR libgcc/113403
	* config/i386/t-heap-trampoline: Add to LIB2ADDEHSHARED
	i386/heap-trampoline.c rather than aarch64/heap-trampoline.c.