cpio: fix ptest-runner dependency

ptest is only meaningful for target. So we need to specify class-target
override to ensure correct dependency.

Also, the above DEPENDS:append:class-targets lacks a leading whitespace,
add it.

(From OE-Core rev: ef705f6969845aa4b28cb2cfb95b0aa0c67c11e3)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/cpio/cpio_2.15.bb

@@ -66,8 +66,8 @@ do_install_ptest_base:append() {
 }
 
 # The tests need to run as a non-root user, so pull in the ptest user
-DEPENDS:append:class-target = "${@bb.utils.contains('PTEST_ENABLED', '1', ' ptest-runner', '', d)}"
-PACKAGE_WRITE_DEPS += "ptest-runner"
+DEPENDS:append:class-target = " ${@bb.utils.contains('PTEST_ENABLED', '1', 'ptest-runner', '', d)}"
+PACKAGE_WRITE_DEPS:append:class-target = " ${@bb.utils.contains('PTEST_ENABLED', '1', 'ptest-runner', '', d)}"
 
 RDEPENDS:${PN}-ptest += "ptest-runner"