ktlint-cli baseline file should not contain absolute filenames

[paul-dingemans]

Ktlint CLI expects the baseline file to contain errors stored per relative file. Instead the errors are store for absolute filenames. As a result Ktlint CLI does not suppress the errors for a baseline that it has created.

Reproduce:

1. Create a file Foo.kt containing code below:

fun Foo() = "foo"

2. Remove baseline.xml
3. Create new baseline.xml with ktlint --baseline=baseline.xml. Baseline contains an error for a file with an absolute path:

<?xml version="1.0" encoding="utf-8"?>
<baseline version="1.0">
    <file name="/some/absolute/path/project/src/main/kotlin/Foo.kt">
        <error line="1" column="5" source="standard:function-naming" />
    </file>
</baseline>

4. Rerun ktlint --baseline=baseline.xml and note that the error is reported while it should have been suppressed.