fix libbeat stress-tests (#37873)

(cherry picked from commit 3912c08)

libbeat/scripts/Makefile

@@ -46,7 +46,7 @@ export PATH := ./bin:$(PATH)
 GOFILES = $(shell find . -type f -name '*.go' 2>/dev/null)
 GOFILES_NOVENDOR = $(shell find . -type f -name '*.go' -not -path "*/vendor/*" 2>/dev/null)
 GOFILES_ALL = $(GOFILES) $(shell find $(ES_BEATS) -type f -name '*.go' 2>/dev/null)
-GOPACKAGES_STRESSTESTS=$(shell find . -name '*.go' 2>/dev/null | xargs grep -l '\+build.*stresstest' | xargs -n1 dirname | uniq)
+GOPACKAGES_STRESSTESTS=$(shell find . -type d \( -name "stress" \) 2>/dev/null)
 SHELL=bash
 ES_HOST?=elasticsearch
 ES_PORT?=9200