redhat-ci: build and test in a fedora container

The upstream tests are being run on Debian rather than distro-specific
containers because there is no golang compiler on AH to compile
gen_dockerfile.go. We should consider porting it to e.g. python in the
future, but for now, we can work around this by building the Dockerfile
in a container.

Author: jlebon

.redhat-ci.yml

@@ -4,4 +4,6 @@ host:
     ram: 4096
 
 tests:
-  - make test
+  - docker run --rm --privileged -v $PWD:/code --workdir /code fedora:25
+    sh -c 'dnf install -y golang && (go run ./distros/gen_dockerfile.go > f)'
+  - make test DOCKERFILE=$(cat f)

Makefile

@@ -5,7 +5,7 @@ DOCKER_GRAPHDRIVER := $(if $(DOCKER_GRAPHDRIVER),$(DOCKER_GRAPHDRIVER),$(shell d
 
 # get OS/Arch of docker engine
 DOCKER_OSARCH := $(shell bash -c 'source hack/make/.detect-daemon-osarch && echo $${DOCKER_ENGINE_OSARCH:-$$DOCKER_CLIENT_OSARCH}')
-DOCKERFILE := $(shell go run ./distros/gen_dockerfile.go)
+DOCKERFILE ?= $(shell go run ./distros/gen_dockerfile.go)
 
 # env vars passed through directly to Docker's build scripts
 # to allow things like `make KEEPBUNDLE=1 binary` easily