[U-Boot] Buildman Kconfig issue with consecutive builds

[Schrempf Frieder]

Hi,

I'm having some trouble using buildman to test the impact of some 
Kconfig cleanup patches ([1]).

The patches introduce a new CONFIG_SPL_* option and I try to find out 
which defconfigs need to be fixed, by comparing build sizes.

Now when I added a patch to fix a defconfig I noticed that buildman 
wouldn't report the expected size changes and upon looking more closely 
I found that the added Kconfig options are still missing in u-boot-spl.cfg.

The strange thing is, that when I try to build only the last commit then 
the Kconfig options are there, which is why I suspect a bug in buildman 
not handling Kconfig changes correctly with consecutive builds.

Can anyone have a look what is wrong or how I can debug this issue?

The issue can be reproduced with the branch at [1], running:

buildman -b spi_flash_kconfig_cleanup_3 --step 0 xilinx_zynqmp_virt

for a build where the added Kconfig options are missing in the resulting 
u-boot-spl.cfg.

And:

buildman -b spi_flash_kconfig_cleanup_3^..spi_flash_kconfig_cleanup_3 
xilinx_zynqmp_virt

for a build of only the last commit with expected output.

Thanks,
Frieder

[1]: https://github.com/fschrempf/u-boot/commits/spi_flash_kconfig_cleanup_3