CompatHelper: bump compat for LLVM to 7, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the LLVM package from 6.1 to 6.1, 7. This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry. It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.64%. Comparing base (b7c96de) to head (197bf10). Report is 4 commits behind head on main.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1420 +/- ## ========================================== + Coverage 69.95% 70.64% +0.68% ========================================== Files 29 29 Lines 10488 10474 -14 ========================================== + Hits 7337 7399 +62 + Misses 3151 3075 -76 ```

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