libpayload/Makefile.payload: Revise config strategy

Payloads often just use one of the defconfigs for libpayload. When
the `Makefile.payload` was introduced, it also added dependencies
to pass a `make oldconfig` or `make defconfig` for the payload on
to libpayload. Turned out, this creates some dependency madness
when, for instance, `make oldconfig` gets called without a libpay-
load `.config` available, or when we try to include the `.config`
in the `Makefile`.

To make things worse, Kconfig's `Makefile` that is imported from
Linux contains some rarely used paths that are generally incompa-
tible to our environment. So let's get rid of the hard-to-control
automatism.

Payloads that don't want to use a libpayload defconfig need to
clear the `$(LIBPAYLOAD_DEFCONFIG)` variable and manually run
the respective config target to generate a `.config`. To fully
support this, the rule to create a `.config` via `defconfig` is
guarded by `$(LIBPAYLOAD_DEFCONFIG)`. Otherwise we'd have a
spurious, broken recipe when the variable is unset.

We keep the option to call libpayload targets with an `lp-` prefix
for convenience. The existing, explicit targets `lp-defconfig` and
`lp-oldconfig` are replaced with a pattern match, so all config
and other targets should work.

Change-Id: Ie3fcce58d98e248c7182cd47f2a797fe066dd18a
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62273
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Thomas Heijligen <src@posteo.de>

0 files changed, 0 insertions, 0 deletions