xmlto: only target requires coreutils

xmlto: only target requires coreutils

The coreutils added to RDEPENDS was for tail command which is everywhere
on the build host, so only add it to target. There was a side effect if
coreutils-native was build, when its commands install to sysroots, they
would be removed during rebuild, and cause other recipes fail to build:

/path/to/tmp/sysroots/x86_64-linux/usr/bin/mkdir -p lib/sys
make: /path/to/tmp/sysroots/x86_64-linux/usr/bin/mkdir: Command not found

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>