Bug: kbuild always rebuilds compressed images on ARM

[Russell King - ARM Linux]

Hi,

I've noticed that kbuild always rebuilds the compressed piggy image
on ARM.  Here's the output from running make with V=2:

  CALL    /home/rmk/git/linux-rmk/scripts/checksyscalls.sh - due to target missing
  CHK     include/generated/compile.h
  Kernel: arch/arm/boot/Image is ready
  Building modules, stage 2.
  LZO     arch/arm/boot/compressed/piggy.lzo - due to command line change
  MODPOST 17 modules - due to target is PHONY
  AS      arch/arm/boot/compressed/piggy.lzo.o - due to: arch/arm/boot/compressed/piggy.lzo
  LD      arch/arm/boot/compressed/vmlinux - due to: arch/arm/boot/compressed/piggy.lzo.o
  OBJCOPY arch/arm/boot/zImage - due to: arch/arm/boot/compressed/vmlinux
  Kernel: arch/arm/boot/zImage is ready

and with V=1:

...
make -f /home/rmk/git/linux-rmk/scripts/Makefile.build obj=arch/arm/boot/compressed arch/arm/boot/compressed/vmlinux
make -f /home/rmk/git/linux-rmk/scripts/Makefile.modpost
  find .tmp_versions -name '*.mod' | xargs -r grep -h '\.ko$' | sort -u | sed 's/\.ko$/.o/' | scripts/mod/modpost -m -a -o /home/rmk/git/build/imx6/Module.symvers    -S  -s -T -
  (cat arch/arm/boot/compressed/../Image | lzop -9 && printf \\010\\224\\034\\002) > arch/arm/boot/compressed/piggy.lzo || (rm -f arch/arm/boot/compressed/piggy.lzo ; false)
make -f /home/rmk/git/linux-rmk/scripts/Makefile.fwinst obj=firmware __fw_modbuild
...

The arch/arm/boot/compressed/.piggy.lzo.cmd file contains this:

cmd_arch/arm/boot/compressed/piggy.lzo := (cat arch/arm/boot/compressed/../Image | lzop -9 && printf \\\\010\\\\224\\\\034\\\\002) > arch/arm/boot/compressed/piggy.lzo || (rm -f arch/arm/boot/compressed/piggy.lzo ; false)

Any ideas why it thinks that the command has changed?

Thanks.