[U-Boot] [PATCH v4] SPL: Makefile: Build a separate autoconf.mk for SPL

[York Sun <yorksun@freescale.com>]

On 08/16/2013 12:14 AM, ying.zhang at freescale.com wrote:
> From: Ying Zhang <b40530@freescale.com>
> 
> SPL defines CONFIG_SPL_BUILD but this does not percolate to the autoconf.mk Makefile.
> As a result the build breaks when CONFIG_SPL_BUILD is used in the board-specific include
> header file. With this, there is a possibility of having a CONFIG option defined in the
> header file but not defined in the Makefile causing all kinds of build failure and problems.
> 
> It also messes things for up, for example, when one might want to undefine options to
> keep the SPL small and doesn't want to be stuck with the CONFIG options used for U-boot.
> Lastly, this also avoids defining special CONFIG_SPL_ variables for cases where some
> options are required in U-boot but not in SPL.
> 
> We add a spl-autoconf.mk rule that is generated for SPL with the CONFIG_SPL_BUILD flag
> and conditionally include it for SPL builds.
> 
> Signed-off-by: Ying Zhang <b40530@freescale.com>

This patch changes Makefile and config.mk. I will need an ack from Tom
before I can apply this patch to 85xx/master.

York