Where the issue happened:
cobblepot-paladin

When the issue started:
The build of package sys-boot/rpi-u-boot has been failing since Build 158 of 05/31/2017 (see https://chromegw.corp.google.com/i/chromeos/builders/cobblepot-paladin?numbuilds=100.)

Suspicious CLs:
 - https://chrome-internal-review.googlesource.com/c/383818/
 - https://chrome-internal-review.googlesource.com/c/384015/ seem to be the causes.

Build error messages:
rpi-u-boot-2017.05-r1: make[2]: *** [/build/cobblepot/tmp/portage/sys-boot/rpi-u-boot-2017.05-r1/work/u-boot-2017.05/scripts/Makefile.autoconf:79: u-boot.cfg] Error 1
rpi-u-boot-2017.05-r1: make[2]: *** [/build/cobblepot/tmp/portage/sys-boot/rpi-u-boot-2017.05-r1/work/u-boot-2017.05/scripts/Makefile.autoconf:50: include/autoconf.mk.dep] Error 1
rpi-u-boot-2017.05-r1: make[2]: Target '__all' not remade because of errors.
rpi-u-boot-2017.05-r1: make[1]: *** No rule to make target 'include/config/auto.conf', needed by 'include/config/uboot.release'.
rpi-u-boot-2017.05-r1:   CHK     include/generated/timestamp_autogenerated.h
rpi-u-boot-2017.05-r1:   GEN     ./Makefile
rpi-u-boot-2017.05-r1: make[1]: *** No rule to make target '/build/cobblepot/tmp/portage/sys-boot/rpi-u-boot-2017.05-r1/work/u-boot-2017.05/arch//cpu/u-boot.lds', needed by 'u-boot.lds'.
rpi-u-boot-2017.05-r1:   UPD     include/generated/timestamp_autogenerated.h
rpi-u-boot-2017.05-r1: make[1]: Target 'all' not remade because of errors.
rpi-u-boot-2017.05-r1: make[1]: Leaving directory '/build/cobblepot/tmp/portage/sys-boot/rpi-u-boot-2017.05-r1/work/build'
rpi-u-boot-2017.05-r1: make: *** [Makefile:150: sub-make] Error 2
rpi-u-boot-2017.05-r1: make: Target 'all' not remade because of errors.
rpi-u-boot-2017.05-r1:  * ERROR: sys-boot/rpi-u-boot-2017.05-r1::loonix-private failed (compile phase):
rpi-u-boot-2017.05-r1:  *   emake failed