Change in coreboot[master]: libpayload/defconfig: enable vboot Lib Build

[Jakub Czapiga (Code Review)]

Attention is currently required from: Bora Guvendik, Anil Kumar K, Selma Bensaid, Tim Wawrzynczak, Julius Werner, Balaji Manigandan.
Jakub Czapiga has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63240 )

Change subject: libpayload/defconfig: enable vboot Lib Build
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Patch Set 5: -Code-Review

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/63240/comment/03030aba_7f206112 
PS3, Line 9: #3461454
> We require to build Coreboot (with Depthcharge) outside the ChromeOS SDK, with default configs in coreboot

May I ask, why the default configs? defconfig is not a mean to make everything work, but a minimal starting point of some kind.
> we hit a compilation error after this new change

Well, that's expected. Depthcharge is meant to be linked with libpayload built with `CONFIG_LP_CHROMEOS=y`. What if there will be more stuff that is expected by Depthcharge only, and not other payloads? We do not want to unnecessarily inflate defconfig, because that way we can enable everything by default anyway.
> We wanted to avoid creation of multiple configs for each board.

You can avoid this by simply appending `CONFIG_LP_CHROMEOS=y` to libpayload dotconfig before its compilation. Why not to add it for boards using Depthcharge as a payload?

Or, as Julius said, you can fix payloads/external/depthcharge/Makefile.inc to append `CONFIG_LP_CHROMEOS=y` to `$(libpayload_dir)/.config` after copying it, if this line is not found in the config file.

Example:
  $(libpayload_install_dir): $(project_dir)
          test -f $(libpayload_config) || \
                  (echo "Error: $(libpayload_config) is not present" && \
                  false)
          echo $(DEPTHCHARGE_LIBPAYLOAD_MSG)
          cp $(libpayload_config) $(libpayload_dir)/.config
          grep -q '^\s*CONFIG_LP_CHROMEOS=' $(libpayload_dir)/.config || \
                  echo -e "CONFIG_LP_CHROMEOS=y" >> $(libpayload_dir)/.config
          $(MAKE) -C $(libpayload_dir) olddefconfig
          $(MAKE) -C $(libpayload_dir)
          $(MAKE) -C $(libpayload_dir) install DESTDIR=$(libpayload_install_dir)