[Issue 21119] Code coverage checker is not instrumenting backend source files

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21119

moonlightsentinel at disroot.org changed:

           What    |Removed                     |Added
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                 CC|                            |moonlightsentinel at disroot.o
                   |                            |rg

--- Comment #1 from moonlightsentinel at disroot.org ---
Probably because the backend is compiled with `-betterC` which apparently
breaks `-cov`.

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