util/build_with_clang: Add option to remove build directory
util/build_with_clang: Add option to remove build directory

By default remove the build directory, but allow disabling it with a
flag.

BRANCH=none
BUG=b:172020503
TEST=./util/build_with_clang.py

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: I0342768da9e340aa4d84bb695cc97550e305326d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4026667
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>
Code-Coverage: Zoss <345cf107e82c70959d46f59d98bddc98ce458aff@prod.google.com>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec