findutils: Fix ptest dependency issue

The options used with 'od' don't work with our busybox config.
Add a dependency on the full utility from coreutils to fix execution
in minimal images.

(From OE-Core rev: 027f0997bd9ba68a86000e91ad81fcf9ea1a4f89)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/findutils/findutils_4.9.0.bb

@@ -14,7 +14,8 @@ CACHED_CONFIGUREVARS += "gl_cv_func_wcwidth_works=yes"
 
 EXTRA_OECONF += "ac_cv_path_SORT=${bindir}/sort"
 
-RDEPENDS:${PN}-ptest += "bash sed grep"
+# need od from coreutils for -t option
+RDEPENDS:${PN}-ptest += "bash sed grep coreutils"
 
 do_install_ptest:class-target() {
 	mkdir -p ${D}${PTEST_PATH}/tests/