Access to source root

[pulanski]

How does one go about getting access to the source root directory from which buck2 is being invoked. When using Bazel, there is an environment variable BUILD_WORKSPACE_DIRECTORY that can be used to get the location of the source root.

[krallin]

Do note that in action execution, the working directory will be the project root (and all paths we produce are relative to it).

[ndmitchell]

@pulanski - what are you trying to do that requires this information? As @krallin usually you don't need it since you have the working directory. But interested in your use case.