Add logging statement to `build-service-pex-files` target
This is to increase visibility in Buildkite logs.
@@ -171,6 +171,7 @@ build-test-unit-rust:
.PHONY: build-service-pex-files
build-service-pex-files: ## Build all PEX files needed by Grapl SaaS services
+ @echo "--- Building Grapl service PEX files"
./pants --tag="service-pex" package ::
.PHONY: build-e2e-pex-files
