O= compilation failure in 2.6.21-rc

[Christoph Hellwig]

looks like 2.6.21-rc4 doesn't compile anymore when using objdir !=
srcdir.  The message is:

WRAP    arch/powerpc/boot/zImage.pseries
powerpc64-linux-ld: cannot open linker script file
arch/powerpc/boot/zImage.lds: No such file or directory
arch/powerpc/boot/zImage.pseries: No such file or directory

works fine for either building in the source dir or just doing a make
vmlinux instead of make so that the zImage wrapper isn't built.