[oe] [RFC] _target suffix

[Frans Meulenbroeks]

It is possible to override settings for e.g. native by adding _native
to a rule or variable.
However, it is not possible to state that a variable or action is only
for the target.

To me it makes sense to have e.g. _target as default suffix so one can e.g. say:
DEPENDS = "x y z"
DEPENDS_target += "t-native"

BBCLASSEXTEND "native"

(the other way would be:
DEPENDS = "x y z t-native "
DEPENDS_virtclass-native = "x y z"

but i think the former is more readable and more error proof.

(btw the above scenario is typically a situation in recipe t which
want to depend on its own native, but the native of course cannot
depend on itself or on -native-native).

Note that although this is probably not too difficult I am not sure
that my pythonese is good enough to add this.
Any suggestion/implementation/whatever is appreciated.

FM