Convert C++ Example to Docker Build Pattern

[markmandel]

While this does make it a longer build time, it makes it easier to get started with the C++ example because there is no tooling dependencies other than Docker (Make is even optional, it just sets the default arguments up).

Also provides an end to end example of compiling the SDK, installing it and then using it with another C++ project.

Co-authored-by: @dsazonoff

[googlebot]

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[googlebot]

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👍 The good news is that everyone that needs to sign a CLA (the pull request submitter and all commit authors) have done so. Everything is all good there.

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[markmandel]

/cc @dsazonoff Please confirm you are good with these changes being applied 😄

Also do you see any issues here?

[agones-bot]

Build Succeeded 👏

Build Id: ee4c5c51-b687-443a-9541-8783106643dd

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:0.10.0-eab4045
• image: gcr.io/agones-images/agones-sdk:0.10.0-eab4045
• image: gcr.io/agones-images/agones-ping:0.10.0-eab4045
• Linux C++ SDK (build): agonessdk-0.10.0-eab4045-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-0.10.0-eab4045.zip

A preview of the website (the last 30 builds are retained):

• https://eab4045-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/746/head:pr_746 && git checkout pr_746
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=0.10.0-eab4045

[dsazonoff]

Looks good.

[agones-bot]

Build Succeeded 👏

Build Id: e8216bf0-ef54-4cc9-86a2-3999cf71845e

The following development artifacts have been built, and will exist for the next 30 days:

• image: gcr.io/agones-images/agones-controller:0.10.0-c0dc2b0
• image: gcr.io/agones-images/agones-sdk:0.10.0-c0dc2b0
• image: gcr.io/agones-images/agones-ping:0.10.0-c0dc2b0
• Linux C++ SDK (build): agonessdk-0.10.0-c0dc2b0-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-0.10.0-c0dc2b0.zip

A preview of the website (the last 30 builds are retained):

• https://c0dc2b0-dot-preview-dot-agones-images.appspot.com/

To install this version:

• git fetch https://github.com/GoogleCloudPlatform/agones.git pull/746/head:pr_746 && git checkout pr_746
• helm install install/helm/agones --namespace agones-system --name agones --set agones.image.tag=0.10.0-c0dc2b0