util/testing: Give meaningful error if intel-sec-tools aren't around

Without manual handling, when 3rdparty/intel-sec-tools isn't around,
`make what-jenkins-does` reports only

    go: go.mod file not found in current directory or any parent directory; see 'go help modules'

which isn't meaningful or actionable. Instead check that the go.mod file
exists and bail out with a better error message before trying to run
`go mod vendor`.

Change-Id: I035747746ca5fd54841bd67352044dde12a28185
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57527
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>

0 files changed, 0 insertions, 0 deletions