classes/recipes: Switch to use inherit_defer

Now that bitbake supports the use of inherit_defer, switch all conditional
(variable based) inherits to use this instead. This leads to more a more
deterministic user experience since there is no longer an immediate expansion
and later changes to the variables in question (e.g. a bbappend) are
accounted for.

This patch tries to ensure the behaviour before/after remains as unchanged
as it reasonably can, e.g. by always inherting populate_sdk_base. native
and nativesdk continue to need to be inherited last, hence being used
with inherit_defer in a handful of very specific cases.

(From OE-Core rev: 451363438d38bd4552d5bcec4a92332f5819a5d4)

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

meta/classes/useradd.bbclass

@@ -268,4 +268,4 @@ fakeroot python populate_packages:prepend () {
 # Use the following to extend the useradd with custom functions
 USERADDEXTENSION ?= ""
 
-inherit ${USERADDEXTENSION}
+inherit_defer ${USERADDEXTENSION}