CI: Move single checks to Github, remove dead code ...

Remove support for very old frontend - we were not testing it anyways.
Move the useful checks to another job so they run once.

Fix Issue #1504 ...

Avoid reusing forward ranges.

Add test for Issue 1504

Make test issue1504-envvar-in-path executable

Fix test Issue 1504

Add .no_test to hopefully fix test1504

Added .no_build
Removed .no_test

Test should work now.

Fix test, for good? All bets are off.