Build invocation image locally

Since we are using `docker context` that is not yet released we need to
cross-compile the master branch of the cli on Jenkins for our e2e tests
to run.
This takes a lot of time when not on Linux and it doesn't make sense to
do locally.

With the new Dockerfile.invocation-image it's possible to run
`make invocation-image` and build the invocation image without
recompiling the cli.

Signed-off-by: Djordje Lukic <djordje.lukic@docker.com>

BUILDING.md

@@ -108,6 +108,6 @@ go test -v -run "<TEST_NAME>" .
  for docker/cnab-app-base:v0.6.0-68-g3ae57efdb6-dirty not found"`, it means
  you forgot to rebuild the base invocation image, simply run
 
- ```sh
- $ make -f docker.Makefile invocation-image
- ```
+```sh
+$ make invocation-image
+```

Dockerfile.invocation-image

@@ -0,0 +1,23 @@
+ARG ALPINE_VERSION=3.8
+ARG GO_VERSION=1.11.0
+
+FROM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS build
+ARG DOCKERCLI_VERSION=18.03.1-ce
+ARG DOCKERCLI_CHANNEL=edge
+RUN apk add --no-cache \
+  make
+
+WORKDIR /go/src/github.com/docker/app/
+
+# builder of invocation image entrypoint
+FROM build AS invocation-build
+COPY . .
+ARG EXPERIMENTAL="off"
+RUN make EXPERIMENTAL=${EXPERIMENTAL} bin/cnab-run
+
+ # local cnab invocation image
+FROM alpine:${ALPINE_VERSION} as invocation
+RUN apk add --no-cache ca-certificates
+COPY --from=invocation-build /go/src/github.com/docker/app/bin/cnab-run /cnab/app/run
+WORKDIR /cnab/app
+CMD /cnab/app/run

Makefile

@@ -27,6 +27,8 @@ endif
 GO_BUILD := CGO_ENABLED=0 go build -tags=$(BUILDTAGS) -ldflags=$(LDFLAGS)
 GO_TEST := CGO_ENABLED=0 go test -tags=$(BUILDTAGS) -ldflags=$(LDFLAGS)
 
+CNAB_BASE_INVOCATION_IMAGE_NAME := docker/cnab-app-base:$(BUILD_TAG)
+
 all: bin/$(BIN_NAME) test
 
 check_go_env:
@@ -97,6 +99,9 @@ specification/bindata.go: specification/schemas/*.json
 
 schemas: specification/bindata.go ## generate specification/bindata.go from json schemas
 
+invocation-image:
+	docker build -f Dockerfile.invocation-image $(BUILD_ARGS) --target=invocation -t $(CNAB_BASE_INVOCATION_IMAGE_NAME) .
+
 help: ## this help
 	@awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_-]+:.*?## / {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST) | sort