zephyr: Split twister build and test
zephyr: Split twister build and test

Perform build only and test only twister commands
per build phase.

BUG=None
BRANCH=None
TEST=./twister

Signed-off-by: Al Semjonovs <c3a2ecb550cad1e7d5a943ca6241377f7b43ffc4@google.com>
Change-Id: I1b68d15eea7404d050c7e8cdcdbaaa4e72192c40
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3783230
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@google.com>

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