dash: Respect portage host cc variable

Pass CC_FOR_BUILD to econf. Otherwise it invokes gcc instead of portage
specified HOST/BUILD CC.

Gentoo PR: https://github.com/gentoo/gentoo/pull/16179

BUG=chromium:979916, chromium:991812, chromium:1093606
TEST=CQ

Change-Id: I16d47e6cab4768cb91628635bed1b2478f5474b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2238517
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed