Environment variable MSI_ENDPOINT and IDENTITY_HEADER should be available to pre-build environment

We are using a "PRE_BUILD_COMMAND" to customise the build environment for our Azure Function (Python on Linux)

The script need to access some external resources protected using EntraID-based authentication. It would be helpful if we could use the managed-identity in this process. To do so the pre-build script would need access to the environment variables MSI_ENDPOINT and IDENTITY_HEADER.

Start by tracing how PRE_BUILD_COMMAND is run for Python Azure Functions on Linux and where its pre-build environment is assembled. Verify whether MSI_ENDPOINT and IDENTITY_HEADER are available to that command, and consider the work done when the pre-build script can use both variables for Entra ID authentication.

Written by the indexing model from the issue text.