Symfony version(s) affected: 4.3, 4.4

Description
When using ignoreVCSIgnored as argument with the Symfony Finder, it will construct a regex equivalent of the gitignore pattern. However it seems that when a comment line (prefixed with #) is present in the .gitignore, the regex used to remove comment lines matches every line and thus returns $gitignoreFileContent as empty.

https://github.com/symfony/symfony/blob/4.4/src/Symfony/Component/Finder/Gitignore.php

How to reproduce
At line 30 in Gitignore, the toRegex function will try to remove all lines that are comments. However when doing so, it seems to mismatch the lines and remove all lines. This only happens when there is at least one comment line present.

$gitignoreFileContent = <<<GITIGNORE
# comment 

###> comment

/.idea/
/build/
/vendor/

# comment
GITIGNORE;

$result = preg_replace('/^[^\\\\]*#.*/', '', $gitignoreFileContent);
$desiredResult = preg_replace('/^[^\\\r\n]*#.*/m', '', $gitignoreFileContent);

var_dump($result);
var_dump($desiredResult);

string(0) ""
string(30) "



/.idea/
/build/
/vendor/

"

Possible Solution
If I'm not doing anything wrong and this is indeed a bug, then we could fix this by adjusting the regular expression. Not sure if my given example regex (/^[^\\\r\n]*#.*/m) is the most beautiful solution, but I would gladly make a pull request.

Additional context

<?php

$gitignoreFileContent = <<<GITIGNORE


/.idea/
/build/
/vendor/

GITIGNORE;

$result = preg_replace('/^[^\\\\]*#.*/', '', $gitignoreFileContent);
$desiredResult = preg_replace('/^[^\r\n]*#.*/m', '', $gitignoreFileContent);

var_dump($result);
var_dump($desiredResult);

string(27) "

/.idea/
/build/
/vendor/
"
string(27) "

/.idea/
/build/
/vendor/
"