Since the recent update of Kconfig to the Kconfig infrastructure found
in 2.6.30 kernels, make oldconfig was broken because it didn't
generate the .config.cmd file. This is done by a call to the
conf_write_autoconf() function.
Moreover, this process was also broken because the
conf_get_autoconfig_name() function was reading the environment
variable BUILDROOT_AUTOCONF while the main Makefile is passing it as
KCONFIG_AUTOCONFIG. We also remove the fallback on
"$(BR2_DEPENDS_DIR)/config/auto.conf" since we are not able to expand
BR2_DEPENDS_DIR at this point. Therefore, the KCONFIG_AUTOCONFIG
envionment variable *must* be set.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
