Where does the extra disk space coming from? The 30 symlinks?

yes, and from lines added to Makefile to support this feature.

It's a tiny amount of disk space.

But I agree, having two ways of doing things is just one more thing that can break.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/ec/+/815b1356903306c66b3a433f0daa4577e1182a2e

commit 815b1356903306c66b3a433f0daa4577e1182a2e
Author: Daisuke Nojiri <dnojiri@chromium.org>
Date: Fri Jul 08 20:51:59 2016

Remove Makefile symlinks under board directory

This feature is inconsistent. Not all boards have such a symlink
(for a obvious reason).

This feature is fragile. It's most likely not tested and going to be
broken if not already. Developers won't like it if they have to test
two different ways to build boards before submitting patches.

This feature is not necessary. If you build EC in the standard way
(e.g. make BOARD=samus), these symlinks are not needed.

This feature is wasteful. Extra disk spaces are used and extra lines
are added to Makefile (increasing code complexity slightly).

BUG=chromium:626776
BRANCH=none
TEST=make buildall

Change-Id: Id5444284d773cb0e9225f39abd877441b8f61440
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/359321
Reviewed-by: Randall Spangler <rspangler@chromium.org>

[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/wheatley/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/hoho/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/strago/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/bds/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/pdeval-stm32f072/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/pit/Makefile
[modify] https://crrev.com/815b1356903306c66b3a433f0daa4577e1182a2e/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/big/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/glados_pd/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/lucid/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/elm/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/snoball/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/glados/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/reef/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/chell/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/host/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/rambi/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/cr50/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/discovery/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/servo_v4/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/llama/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/nucleo-f072rb/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/npcx_evb/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/kevin/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/it83xx_evb/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/auron/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/stm32l476g-eval/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/npcx_evb_arm/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/discovery-stm32f072/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/hadoken/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/samus/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/servo_micro/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/samus_pd/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/zinger/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/twinkie/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/jerry/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/ryu/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/plankton/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/amenia/Makefile
[delete] https://crrev.com/9a13c52f30cd50a537b2ceeb2e5a62f398d458b6/board/dingdong/Makefile