std.experimental.logger: file logger should use OS-specific directory separators on each platform

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) reported this on 2022-09-10T09:57:03Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=23330

Description

https://github.com/dlang/phobos/blob/e7cb981fa40bd77647da3dd708c7433724c6ab30/std/logger/filelogger.d#L129

This should use the OS-specific path separator, as on Windows it doesn't strip the path correctly due to using `/`.

[dlangBugzillaToGithub]

andrej.mitrovich (@AndrejMitrovic) commented on 2022-09-10T09:58:15Z

I should say dir separator, not path separator. I'll fix up the issue name.