Add Make variable to change the Go test command

This provides a way to change the formatting of test results. For example, the `gotest.tools/gotestsum` module highlights skipped tests and stores results as JUnit XML files. make check GO_TEST='gotestsum --'

Author: cbandy

Makefile

@@ -63,6 +63,7 @@ DEBUG_BUILD ?= false
 GO ?= go
 GO_BUILD = $(GO_CMD) build -trimpath
 GO_CMD = $(GO_ENV) $(GO)
+GO_TEST ?= $(GO) test
 
 # Disable optimizations if creating a debug build
 ifeq ("$(DEBUG_BUILD)", "true")
@@ -189,17 +190,17 @@ pgo-base-docker: pgo-base-build
 #======== Utility =======
 .PHONY: check
 check:
-$(GO) test -cover ./...
+$(GO_TEST) -cover ./...
 
 # - KUBEBUILDER_ATTACH_CONTROL_PLANE_OUTPUT=true
 .PHONY: check-envtest
 check-envtest: hack/tools/envtest
-KUBEBUILDER_ASSETS="$(CURDIR)/$^/bin" $(GO) test -count=1 -cover -tags=envtest ./...
+KUBEBUILDER_ASSETS="$(CURDIR)/$^/bin" $(GO_TEST) -count=1 -cover -tags=envtest ./...
 
 .PHONY: check-envtest-existing
 check-envtest-existing:
 ${PGO_KUBE_CLIENT} apply -k ./config/dev
-USE_EXISTING_CLUSTER=true $(GO) test -count=1 -cover -tags=envtest ./...
+USE_EXISTING_CLUSTER=true $(GO_TEST) -count=1 -cover -tags=envtest ./...
 ${PGO_KUBE_CLIENT} delete -k ./config/dev