generate_report.sh: Use Jenkins ennvar for default builder job name

This makes it compatible with personal staging job names (e.g.
pfalcon-tf-a-builder).

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: I6b2e5b0c661bd6c8a09b624bb090b2d5e0bb33cb
diff --git a/job/tf-ci-gateway/generate_report.sh b/job/tf-ci-gateway/generate_report.sh
index ac2eb7d..5c958e8 100755
--- a/job/tf-ci-gateway/generate_report.sh
+++ b/job/tf-ci-gateway/generate_report.sh
@@ -21,8 +21,11 @@
 		worker_job="${worker_job:-tf-worker}"
 		lava_job="${lava_job:-tf-build-for-lava}"
 	else
-		worker_job="${worker_job:-tf-a-builder}"
-		lava_job="${lava_job:-tf-a-builder}"
+		# ${TRIGGERED_JOB_NAMES} has hyphens replaced with underscores.
+		# As we know that we use hyphen convention, translate it back.
+		triggered_job=$(echo ${TRIGGERED_JOB_NAMES} | tr "_" "-")
+		worker_job="${worker_job:-${triggered_job}}"
+		lava_job="${lava_job:-${triggered_job}}"
         fi
 
 	"$CI_ROOT/script/gen_test_report.py" \