sanitycheck: fix priority of --extra-args=CONFIG_ over testcase.yaml

sanitycheck takes any "extra_config" list found in the testcase.yaml
file and generates an "overlay" file from it. This file is placed in
the per-test build directory and passed to cmake/kconfig.cmake through a
-DOVERLAY_CONF= option set in the (also) generated sanity-out/Makefile.

This commit moves this generated config overlay to a subdirectory one
level down from the build directory, otherwise kconfig.cmake picks it
up *twice*: once from the -DOVERLAY_CONF= option already mentioned above
and a second time because kconfig.cmake scans the build directory and
blindly picks up ALL files ending with .conf[*]. The second pickup is
problematic because kconfig.cmake currently gives it the top precedence,
even higher than anything the user espressed with --extra-args=CONFIG_*

Here's a quick and simple demonstration of the issue fixed by this
commit:

  cd $ZEPHYR_BASE/samples/net/sockets/net_mgmt/
  sanitycheck -T. -p qemu_x86 -b -v # --extra-args=CONFIG_USERSPACE=y|n
  grep CONFIG_USERSPACE $(find sanity-out/ -name .config)

  .net_mgmt.kernelmode/zephyr/.config: # CONFIG_USERSPACE is not set
    .net_mgmt.usermode/zephyr/.config: CONFIG_USERSPACE=y

  grep 'Merged configuration' $(find sanity-out/ -name build.log)

Without this commit, attemps to override anything with
--extra-args=CONFIG_ are silently dropped on the floor.

For more background this issue was found while using the recipe in
commit message 4afcc0f8af2b

[*] picking up all .conf files is debatable but a much bigger debate
with backward compatibility implications. This small fix makes
absolutely zero difference to anyone or anything not using sanitycheck.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>
2 files changed