Environment variable support to dump the pass pipeline string created by the python experts

[nicolasvasilache]

No description provided.

[13hulk]

@nicolasvasilache Could you please provide more details?

[nicolasvasilache]

Hi @vikasbz

Basically here: https://github.com/google/iree-llvm-sandbox/blob/main/python/core/transforms.py#L15

We would need to print the self.pipeline if some TBD os.getenv is set.

I am unsure about ergonomics atm (e.g. print and exit, or print and continue and risk the string to be lost in other debug info).