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

(From OE-Core rev: 4a0e3ca3733e2b6f3f20065421dbb9da2058014c)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/xmlto/xmlto_0.0.28.bb

@@ -20,10 +20,10 @@ RDEPENDS_${PN} = "docbook-xml-dtd4 \
                   util-linux \
                   libxml2 \
                   bash \
-                  coreutils \
 "
 RDEPENDS_${PN}_append_class-target = " \
                   libxslt-bin \
+                  coreutils \
 "
 CACHED_CONFIGUREVARS += "ac_cv_path_TAIL=${bindir}/tail"