zephyr: migrate slot 0 validation to Kconfig
Handle CONFIG_BOOT_VALIDATE_SLOT0 in mcuboot_config.h, and switch to
setting it with an OVERLAY_CONFIG fragment in the test Makefile.
Signed-off-by: Marti Bolivar <marti@opensourcefoundries.com>
diff --git a/samples/zephyr/overlay-skip-slot0-validate.conf b/samples/zephyr/overlay-skip-slot0-validate.conf
new file mode 100644
index 0000000..dd3b2c2
--- /dev/null
+++ b/samples/zephyr/overlay-skip-slot0-validate.conf
@@ -0,0 +1,3 @@
+# Kconfig overlay for building without validating slot 0.
+
+# CONFIG_BOOT_VALIDATE_SLOT0 is not set