[U-Boot] [U-Boot, V3] Makefile: remove BUILD_TAG from KBUILD_CFLAGS

[Tom Rini <trini@konsulko.com>]

On Wed, Feb 10, 2016 at 03:16:19PM -0700, Stephen Warren wrote:

> From: Stephen Warren <swarren@nvidia.com>
> 
> If BUILD_TAG is part of KBUILD_CFLAGS, then any time the value changes,
> all files get rebuilt. In a continuous integration environment, the value
> will change every build. This wastes time, assuming that incremental
> builds would otherwise occur.
> 
> To solve this, remove BUILD_TAG from KBUILD_CFLAGS and add it to CFLAGS
> for just the one file that uses it. This does have the disadvantage that
> if any other files want to use the flag, we'll need to duplicate this
> custom CFLAGS setup logic. However, it seems unlikely we'll need this.
> 
> An alternative would be to add BUILD_TAG to the "local version" and remove
> the special case code from display_options.c. However, that would affect
> the format of the U-Boot signon message, which may negatively affect
> people looking for specific data there. The approach of using
> file-specific CFLAGS was suggested by Masahiro Yamada.
> 
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> Reviewed-by: Tom Rini <trini@konsulko.com>
> Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Acked-by: Simon Glass <sjg@chromium.org>

Applied to u-boot/master, thanks!

-- 
Tom
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