Fix Issue 21844: makedeps contain non-existing files

[Panke]

There is no reasonable way to track non-existing files (since they could be anywhere where -J, -I points to) and by not tracking them at least the builds won't be always out of date.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	21844	major	makedeps option adds spurious/incorrect dependency

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#13755"

[kinke]

LGTM, thanks! - I consider this a mjaor issue, not a minor one, and would suggest targeting stable, so that it can still make it into v2.099.0.

[Panke]

Rebased onto stable

[ljmf00]

I changed the issue's importance. Buildkite is failing, perhaps due to changing the target branch. Can you force amend the commit and push?