Baseline report should always have forward slashes for path separator.

Author: frankdekker

src/Reports/Baseline.php

@@ -39,7 +39,7 @@ public function generateFileReport($report, File $phpcsFile, $showSources = fals
             foreach ($lineErrors as $colErrors) {
                 foreach ($colErrors as $error) {
                     $out->startElement('violation');
-                    $out->writeAttribute('file', $report['filename']);
+                    $out->writeAttribute('file', str_replace('\\', '/', $report['filename']));
                     $out->writeAttribute('sniff', $error['source']);
                     $out->writeAttribute('signature', $signature);
 

tests/Unit/Reports/BaselineTest.php

@@ -38,7 +38,7 @@ public function testGenerateFileReportEmptyShouldReturnFalse(): void
     public function testGenerateFileReportShouldPrintReport(): void
     {
         $reportData = [
-            'filename' => '/test/foobar.txt',
+            'filename' => '/test\\foobar.txt',
             'errors'   => 1,
             'warnings' => 0,
             'messages' => [5 => [[['source' => 'MySniff']]]],