[GRASS-git] [OSGeo/grass] 191521: ci: Update setting env vars, Ubuntu 20.04 (#1098)

[Vaclav Petras]

  Branch: refs/heads/releasebranch_7_8
  Home:   https://github.com/OSGeo/grass
  Commit: 191521e2360c9845ef54d053e0fd86eaa99d5fef
      https://github.com/OSGeo/grass/commit/191521e2360c9845ef54d053e0fd86eaa99d5fef
  Author: Vaclav Petras <wenzeslaus at gmail.com>
  Date:   2020-11-18 (Wed, 18 Nov 2020)

  Changed paths:
    M .github/workflows/ci.yml
    M .github/workflows/flake8.yml

  Log Message:
  -----------
  ci: Update setting env vars, Ubuntu 20.04 (#1098)

Update how env vars and path var are set in GitHub Actions after change in the API (fixes #1090).

Compile and test also on Ubuntu 20.04.

Use Ubuntu 20.04 for Flake8 tests (ubuntu-20.04 will become ubuntu-latest on GH Actions soon).