add docs for an initial stab at adoptium#957

docs/ARCHITECTURE.md

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+
+# Architecture
+
+Our build farm has a number of major components:
+
+1. Jenkins Build Pipeline Configuration
+1. Adopt build scripts
+1. Supporting libraries
+
+## Process
+
+A rough structure of the build is as follows
+![Structure](images/structure.svg)
+
+### Jenkins Job
+
+#### Regenerate Jobs
+Jenkins CI jobs are generated by the [regeneration pipelines](pipelines/build/regeneration) in Jenkins. The documentation for 
+this process can be found at [regeneration docs](pipelines/build/regeneration/README.md), however they generate the jobs
+at https://ci.adoptopenjdk.net/job/build-scripts/ which are the builds that coordinate the entire process of nightly 
+and release builds.
+
+#### Pipeline Jobs
+These are the initial scripts that are the top level jobs that are invoked, this in turn invokes the downstream build
+jobs for each configuration/platform then coordinates deploying the results to Github. The majority of the code that 
+defines this stage is contained within [build_base_file.groovy](https://github.com/AdoptOpenJDK/openjdk-build/blob/master/pipelines/build/common/build_base_file.groovy).
+
+#### Indiviual Build Jobs
+This are invoked by the parent pipeline job and each build creates the archives/installers for a given platform. The majority
+of this code is defined in [openjdk_build_pipeline.groovy](https://github.com/AdoptOpenJDK/openjdk-build/blob/master/pipelines/build/common/openjdk_build_pipeline.groovy).
+
+#### Build farm scripts
+These are the entry point for the build itself when it executes on the end node. These are cross platform shell scripts
+defined in [build-farm](https://github.com/AdoptOpenJDK/openjdk-build/tree/master/build-farm) and are kicked off by running
+[make-adopt-build-farm.sh](https://github.com/AdoptOpenJDK/openjdk-build/blob/master/build-farm/make-adopt-build-farm.sh).
+This load configuration/setup that is specific to the adopt build farm and the current architecture before 
+invoking the build scripts.
+
+#### Build Scripts
+These are the cross platform scripts that invoke the actual build. When inside the build farm they are executed
+from [make-adopt-build-farm.sh](https://github.com/AdoptOpenJDK/openjdk-build/blob/master/build-farm/make-adopt-build-farm.sh).
+The initial entry point for these scripts is [makejdk-any-platform.sh](https://github.com/AdoptOpenJDK/openjdk-build/blob/master/makejdk-any-platform.sh)
+and the majority of the code for this step is contained within [sbin](https://github.com/AdoptOpenJDK/openjdk-build/tree/master/sbin).
+
+#### adopt-shared-lib
+
+The [adopt-shared-lib](https://github.com/AdoptOpenJDK/openjdk-build/tree/master/pipelines/library/src) is a Groovy library that provides a number of helper classes to the other parts of the build process such
+as a version parser, metadata file and build configuration definitions.