feat(build): Ubuntu image variant support (#490)

* feat(build): Building a ubuntu image

* New tagging format: `version-variant`, example: `1.2.3-slim`
* For backward compatibility with the buildtool system and older versions of Halyard, the alpine image variant keeps the original 'naked' version tag i.e. `1.2.3` in addition to the one with the new format.
* The BOM format doesn't change, it's up to Halyard to append the right `-variant` for a tag to fetch the right image on the registry.
* The Dockerfiles are meant to be used directly for ad-hoc image creation by an end-user and by the existing build system through `cloudbuild.yml`.

* Cloudbuild.yaml is now generic and lives in spinnaker/spinnaker buildtool

Dockerfile.compile

@@ -0,0 +1,6 @@
+FROM gcr.io/spinnaker-marketplace/gradle_cache
+MAINTAINER delivery-engineering@netflix.com
+ENV GRADLE_USER_HOME /gradle_cache/.gradle
+COPY . compiled_sources
+WORKDIR compiled_sources
+RUN ./gradlew --no-daemon igor-web:installDist -x test

Dockerfile.slim

@@ -1,13 +1,7 @@
 FROM openjdk:8-jre-alpine
-
 MAINTAINER delivery-engineering@netflix.com
-
-COPY ./igor-web/build/install/igor /opt/igor
-
+COPY --from=compile /compiled_sources/igor-web/build/install/igor /opt/igor
 RUN apk --no-cache add --update bash
-
 RUN adduser -D -S spinnaker
-
 USER spinnaker
-
 CMD ["/opt/igor/bin/igor"]

Dockerfile.ubuntu

@@ -0,0 +1,7 @@
+FROM ubuntu:bionic
+MAINTAINER delivery-engineering@netflix.com
+COPY --from=compile /compiled_sources/igor-web/build/install/igor /opt/igor
+RUN apt-get update && apt-get -y install openjdk-8-jre-headless wget
+RUN adduser --disabled-login --system spinnaker
+USER spinnaker
+CMD ["/opt/igor/bin/igor"]