Makefile: enable race detection for unit tests (thanos-io#6873)

Let's enable the race detection for unit tests. Closes
thanos-io#4664.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>

Makefile

@@ -314,7 +314,7 @@ test: export THANOS_TEST_ALERTMANAGER_PATH= $(ALERTMANAGER)
 test: check-git install-tool-deps
 	@echo ">> install thanos GOOPTS=${GOOPTS}"
 	@echo ">> running unit tests (without /test/e2e). Do export THANOS_TEST_OBJSTORE_SKIP=GCS,S3,AZURE,SWIFT,COS,ALIYUNOSS,BOS,OCI,OBS if you want to skip e2e tests against all real store buckets. Current value: ${THANOS_TEST_OBJSTORE_SKIP}"
-	@go test -timeout 15m $(shell go list ./... | grep -v /vendor/ | grep -v /test/e2e);
+	@go test -race -timeout 15m $(shell go list ./... | grep -v /vendor/ | grep -v /test/e2e);
 
 .PHONY: test-local
 test-local: ## Runs test excluding tests for ALL  object storage integrations.