test: Add some tests for kconfig.h

The macros in this file are a little confusing and we currently have no
tests to check that they work as expected.

Add some tests which check the macros in C code. Add a few tests which
check that the build errors are generated correctly too, using buildman's
-a option.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/lib/Makefile b/test/lib/Makefile
index d244bb4..7e7922f 100644
--- a/test/lib/Makefile
+++ b/test/lib/Makefile
@@ -2,11 +2,13 @@
 #
 # (C) Copyright 2018
 # Mario Six, Guntermann & Drunck GmbH, mario.six@gdsys.cc
+ifeq ($(CONFIG_SPL_BUILD),)
 obj-y += cmd_ut_lib.o
 obj-y += abuf.o
 obj-$(CONFIG_EFI_LOADER) += efi_device_path.o
 obj-$(CONFIG_EFI_SECURE_BOOT) += efi_image_region.o
 obj-y += hexdump.o
+obj-$(CONFIG_SANDBOX) += kconfig.o
 obj-y += lmb.o
 obj-y += longjmp.o
 obj-$(CONFIG_CONSOLE_RECORD) += test_print.o
@@ -19,3 +21,6 @@
 obj-$(CONFIG_AES) += test_aes.o
 obj-$(CONFIG_GETOPT) += getopt.o
 obj-$(CONFIG_UT_LIB_CRYPT) += test_crypt.o
+else
+obj-$(CONFIG_SANDBOX) += kconfig_spl.o
+endif