An instance is created at the start of a Gradle invocation and discarded at the end of that invocation.

The build session state also includes "cross session" state that is shared with any "nested" sessions that need to be created.
This only happens when the `GradleBuild` task is used. You can mostly ignore the distinction between "cross session" and "build session" state.

### Build tree state

# Create targets for TARGET_OUT_LINUX/binary
# There are two use cases here:
# * Building all docker images (generally in CI). In this case we want to build everything at once, so they share work
# * Building a single docker image (generally during dev). In this case we just want to build the single binary alone
BUILD_ALL ?= true
define build-linux
.PHONY: $(TARGET_OUT_LINUX)/$(shell basename $(1))