Support architecture targeted builds (aws#837)

This reworks much of the Makefile and, to a lesser extent, the
Dockerfiles for building the CNI plugins for other platforms.

Additional clean up work is included as well as this was combed
through to support these builds.

Including:

- ARCH resolver to identify the ARCH (GOARCH styled) to pass around
- Updated ARCH and GOARCH references throughout to support
  against other ARCHes
- Make base container build appropriately for ARCH
  - Docker explicit multiarch references in targets and Dockerfiles
  - Updated related container images to allow testing where possible
- Eliminate ./tmp usage with tar unpacking from a pipe
- Clean up and consistent call sites all around
   - Reconciled image naming
   - Updated stale golang images references
- Added docstrings for reference

.circleci/config.yml

@@ -5,28 +5,46 @@ orbs:
   aws-cli: circleci/aws-cli@0.1.19
   k8s: circleci/kubernetes@0.11.0
 
-jobs:
-  build:
+references:
+  build_job: &build
     docker:
       - image: circleci/golang:1.13-stretch
     working_directory: /go/src/github.com/{{ORG_NAME}}/{{REPO_NAME}}
-    environment:
+    environment: &env
       GO111MODULE: "on"
     steps:
       - checkout
       - run: go get -u golang.org/x/lint/golint
       - run: go get -u golang.org/x/tools/cmd/goimports
       - run: make check-format
-      - run: make build-linux
-      - run: make lint
+      - run: make build-linux "ARCH=$ARCH"
+      # TODO: Make lint a hard-check once baselined
+      - run: make lint LINT_FLAGS=
       - run: make vet
-      - run: make unit-test
+      # TODO: Enable architecture specific unit-test when Circle CI supports it!
+      - run: make unit-test ARCH=amd64
+
+jobs:
+  build_x86_64:
+    <<: *build
+    environment:
+      <<: *env
+      # Target the GOARCH for x86_64
+      ARCH: amd64
+
+  build_aarch64:
+    <<: *build
+    environment:
+      <<: *env
+      # Target the GOARCH for aarch64
+      ARCH: arm64
+
   integration_test:
     docker:
       - image: circleci/golang:1.13-stretch
     working_directory: /go/src/github.com/{{ORG_NAME}}/{{REPO_NAME}}
     environment:
-      GO111MODULE: "on"
+      <<: *env
       RUN_CONFORMANCE: "true"
     steps:
       - checkout
@@ -47,11 +65,13 @@ workflows:
   version: 2
   check:
     jobs:
-      - build
+      - build_x86_64
+      - build_aarch64
       - hold:
           type: approval
           requires:
-            - build
+            - build_x86_64
+            - build_aarch64
       - integration_test:
           requires:
             - hold

.dockerignore

@@ -1,4 +1,6 @@
 aws-cni
 aws-k8s-agent
+cni-metrics-helper
+grpc-health-probe
 portmap
-cni-metrics-helper/cni-metrics-helper
+routed-eni-cni-plugin

.gitignore

@@ -7,6 +7,6 @@ verify-network
 .idea/
 *.iml
 .DS_Store
-cni-metrics-helper/cni-metrics-helper
 portmap
 grpc-health-probe
+cni-metrics-helper