mini-os: use correct objcopy
mini-os: remove unused variable from gic code, silencing warnings
Fixed compiler errors

xenbus/xenbus.c: In function 'xenbus_transaction_start':
xenbus/xenbus.c:683:5: error: format '%u' expects argument of type 'unsigned int *', but argument 3 has type 'xenbus_transaction_t *' [-Werror=format=]
     sscanf((char *)(rep + 1), "%u", xbt);
     ^
xenbus/xenbus.c: In function 'xenbus_get_self_id':
xenbus/xenbus.c:780:5: error: format '%d' expects argument of type 'int *', but argument 3 has type 'domid_t *' [-Werror=format=]
     sscanf(dom_id, "%d", &ret);
Use -mfloat-abi=hard

Avoids build error:

[...]
ld -r   /root/minios-arm/extras/mini-os/arch/arm/arm32.o  /root/minios-arm/extras/mini-os/drivers/gic.o /root/minios-arm/extras/mini-os/lib/fdt/fdt.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_empty_tree.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_ro.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_rw.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_strerror.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_sw.o /root/minios-arm/extras/mini-os/lib/fdt/fdt_wip.o /root/minios-arm/extras/mini-os/events.o /root/minios-arm/extras/mini-os/gntmap.o /root/minios-arm/extras/mini-os/gnttab.o /root/minios-arm/extras/mini-os/hypervisor.o /root/minios-arm/extras/mini-os/time.o /root/minios-arm/extras/mini-os/kernel.o /root/minios-arm/extras/mini-os/lock.o /root/minios-arm/extras/mini-os/main.o /root/minios-arm/extras/mini-os/mm.o /root/minios-arm/extras/mini-os/sched.o /root/minios-arm/extras/mini-os/lib/ctype.o /root/minios-arm/extras/mini-os/lib/printf.o /root/minios-arm/extras/mini-os/lib/stack_chk_fail.o /root/minios-arm/extras/mini-os/lib/string.o /root/minios-arm/extras/mini-os/lib/sys.o /root/minios-arm/extras/mini-os/lib/xmalloc.o /root/minios-arm/extras/mini-os/lib/xs.o /root/minios-arm/extras/mini-os/xenbus/xenbus.o /root/minios-arm/extras/mini-os/console/console.o /root/minios-arm/extras/mini-os/console/xencons_ring.o -L/root/minios-arm/extras/mini-os/arch/arm -larm32  -o /root/minios-arm/extras/mini-os/mini-os.o
ld: error: /root/minios-arm/extras/mini-os/lib/fdt/fdt.o uses VFP register arguments, /root/minios-arm/extras/mini-os/mini-os.o does not
ld: failed to merge target specific data of file /root/minios-arm/extras/mini-os/lib/fdt/fdt.o
ld: error: /root/minios-arm/extras/mini-os/lib/fdt/fdt_empty_tree.o uses VFP register arguments, /root/minios-arm/extras/mini-os/mini-os.o does not
ld: failed to merge target specific data of file /root/minios-arm/extras/mini-os/lib/fdt/fdt_empty_tree.o
ld: error: /root/minios-arm/extras/mini-os/lib/fdt/fdt_ro.o uses VFP register arguments, /root/minios-arm/extras/mini-os/mini-os.o does not
ld: failed to merge target specific data of file /root/minios-arm/extras/mini-os/lib/fdt/fdt_ro.o
ld: error: /root/minios-arm/extras/mini-os/lib/fdt/fdt_rw.o uses VFP register arguments, /root/minios-arm/extras/mini-os/mini-os.o does not
ld: failed to merge target specific data of file /root/minios-arm/extras/mini-os/lib/fdt/fdt_rw.o
ld: error: /root/minios-arm/extras/mini-os/lib/fdt/fdt_strerror.o uses VFP register arguments, /root/minios-arm/extras/mini-os/mini-os.o does not
[...]