envtools: make them build again

In v2024.10, "make envtools" is broken for at least these defconfigs:

   am335x_evm_defconfig
   rpi_3_defconfig
   rpi_4_defconfig
   mx7dsabresd_defconfig
   wandboard_defconfig
   imx8mp_evk_defconfig

The only defconfig we use for which it is not broken is
stm32mp13_defconfig. They all work just fine in v2024.07.

The symptoms are slightly different, but all related to the fact that
some transitively included header uses IS_ENABLED or CONFIG_IS_ENABLED
without linux/kconfig.h having already been included.

A simple git bisect doesn't produce anything sensible, it ends up at
3a9f642ca9 (crypto: nuvoton: npcm_sha: Support SHA 384/512) which
clearly has nothing to do with this. But digging deeper, one
eventually finds 0f92fa4560 ("env: Remove <common.h> and add needed
includes").

So at first I tried adding "#include <linux/kconfig.h>" in
include/env_default.h and include/env_flags.h. That fixes it for some,
but not all, of the above. For example rpi_3_defconfig still fails,
then in log.h complaining about BIT() and u8 not being defined. At
least BIT() is should have gotten from bitops.h, except that that's
behind ifdef __KERNEL__, so not set for the envtools build.

It turns out that the envtools source code in fw_env_private.h already
has some hackery to deal with all this, in the form of the __ASSEMBLY__
games it plays before including config.h. It seems that if we just
make sure to do that include early enough, so that config.h is indeed
parsed with that __ASSEMBLY__ hackery in place, everything builds
fine.

Fixes: 0f92fa4560 ("env: Remove <common.h> and add needed includes")
Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>

tools/env/fw_env.c

@@ -9,6 +9,8 @@
 
 #define _GNU_SOURCE
 
+#include "fw_env_private.h"
+
 #include <compiler.h>
 #include <env.h>
 #include <errno.h>
@@ -39,7 +41,6 @@
 
 #include <mtd/ubi-user.h>
 
-#include "fw_env_private.h"
 #include "fw_env.h"
 
 struct env_opts default_opts = {