Makefile: allow filtering e2e tests

This commit enables the filtering of e2e tests that should be run when
using the Makefile's `e2e` target through the specification of the
`BASH_UNIT_FLAGS` environment variable. The value of this variable will
be passed as arguments to the `bash_unit` command, enabling filtering of
tests.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

Makefile

@@ -43,6 +43,7 @@ EMBEDMD_BINARY := bin/embedmd
 KIND_BINARY := $(shell pwd)/bin/kind
 KUBECTL_BINARY := $(shell pwd)/bin/kubectl
 BASH_UNIT := $(shell pwd)/bin/bash_unit
+BASH_UNIT_FLAGS :=
 
 BUILD_IMAGE ?= golang:1.16.5-alpine
 BASE_IMAGE ?= alpine:3.13
@@ -208,7 +209,7 @@ $(BASH_UNIT):
 	chmod +x $@
 
 e2e: container $(KIND_BINARY) $(KUBECTL_BINARY) $(BASH_UNIT) bin/$(OS)/$(ARCH)/kgctl
-	KILO_IMAGE=$(IMAGE):$(ARCH)-$(VERSION) KIND_BINARY=$(KIND_BINARY) KUBECTL_BINARY=$(KUBECTL_BINARY) KGCTL_BINARY=$(shell pwd)/bin/$(OS)/$(ARCH)/kgctl $(BASH_UNIT) ./e2e/setup.sh ./e2e/full-mesh.sh ./e2e/location-mesh.sh ./e2e/teardown.sh
+	KILO_IMAGE=$(IMAGE):$(ARCH)-$(VERSION) KIND_BINARY=$(KIND_BINARY) KUBECTL_BINARY=$(KUBECTL_BINARY) KGCTL_BINARY=$(shell pwd)/bin/$(OS)/$(ARCH)/kgctl $(BASH_UNIT) $(BASH_UNIT_FLAGS) ./e2e/setup.sh ./e2e/full-mesh.sh ./e2e/location-mesh.sh ./e2e/teardown.sh
 
 header: .header
 	@HEADER=$$(cat .header); \