kristenk authored Dec 14, 2019 and Oleg Grenrus committed Dec 18, 2019

Fixes #6417.

Changes in this commit:

- Set the --lib flag so that the benchmark works for packages with libraries or
  executables.
- Set --ignore-project to prevent cabal projects from affecting the results.
- Handle four types of cabal errors that were introduced by v2-install.
- Use +nowrap to simplify parsing of cabal errors.