libchromeos: process.cc fail cleanly when no arguments are specified.

If we attempt to spawn a process to run an executable, fail early
instead of waiting for the call to fail.

BUG=None
TEST=unittests pass.
TEST=trybot run on daisy, link, lumpy, mips.

Change-Id: I1742101eb47787b948b20d4129a8b1893dba0568
Reviewed-on: https://chromium-review.googlesource.com/287864
Reviewed-by: Bertrand Simonnet <bsimonnet@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
Trybot-Ready: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
2 files changed