Documentation/process/changes.rst notes the minimal GNU Make version,
but it is not checked anywhere.

We could check $(MAKE_VERSION), but another simple way is to check
$(.FEATURES) since the feature list always grows.

GNU Make 3.81 expands $(.FEATURES) to:
  target-specific order-only second-expansion else-if archives jobserver check-symlink

GNU Make 3.82 expands $(.FEATURES) to:
  target-specific order-only second-expansion else-if shortest-stem undefine archives jobserver check-symlink

To ensure Make >= 3.82, you can check either 'shortest-stem' or
'undefine'.

This way is not always possible. For example, Make 4.0 through 4.2 have
the same set of $(.FEATURES). At that point, we will need to come up
with a different approach.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>