Feature request: debug mode

[luigibk]

Add option and code to allow debugger-based debugging to use with a tool like delve to inspect what is happening in a provider as it is happening.

Overview

A detailed explanation is available in this section of the Terraform plugin sdk documentation:
debugger-based-debugging
This would allow to set breakpoints to pause execution of the provider and examine the values of variables and it would be useful to investigate reproducible bugs

Possible Implementation

Update main.go + Makefile.build to introduce the command line and compilation options needed.

Context

I found this feature useful while investigating a SIGSEGV caused by a nil pointer being dereferenced.

Your Environment

This would be only executed ad-hoc when necessary.

[tobio]

Fixed by #430