Build Postgres bundled in Docker image from source to achieve parity with the AMI

[pcnc]

The official Postgres Docker image, off of which we base our Docker builds, is built using different compiler flags than the ones we're using to build Postgres in the AMI, which can create problems for users developing locally and then moving to projects created on the platform if they're using features enabled by default by the the Docker image, as they're missing in the AMI which is deployed on the platform.