x86: Use $(OBJDUMP) instead of plain objdump

commit e6023367d7 'x86, kaslr: Prevent .bss from overlaping initrd'
broke the cross compile of x86. It added a objdump invocation, which
invokes the host native objdump and ignores an active cross tool
chain.

Use $(OBJDUMP) instead which takes the CROSS_COMPILE prefix into
account.

[ tglx: Massage changelog and use $(OBJDUMP) ]

Fixes: e6023367d7 'x86, kaslr: Prevent .bss from overlaping initrd'
Signed-off-by: Chris Clayton <chris2553@googlemail.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Junjie Mao <eternal.n08@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/54705C8E.1080400@googlemail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/boot/compressed/Makefile

@@ -76,7 +76,7 @@ suffix-$(CONFIG_KERNEL_XZ)	:= xz
 suffix-$(CONFIG_KERNEL_LZO) 	:= lzo
 suffix-$(CONFIG_KERNEL_LZ4) 	:= lz4
 
-RUN_SIZE = $(shell objdump -h vmlinux | \
+RUN_SIZE = $(shell $(OBJDUMP) -h vmlinux | \
 	     perl $(srctree)/arch/x86/tools/calc_run_size.pl)
 quiet_cmd_mkpiggy = MKPIGGY $@
       cmd_mkpiggy = $(obj)/mkpiggy $< $(RUN_SIZE) > $@ || ( rm -f $@ ; false )