[Bug 51687] New: GetMappedFileNameA/W implementation breaks RiotClient updates.

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51687

Bug ID: 51687
           Summary: GetMappedFileNameA/W implementation breaks RiotClient
                    updates.
           Product: Wine
           Version: 6.15
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 70554
  --> https://bugs.winehq.org/attachment.cgi?id=70554
trace log

Since wine (vanilla or staging) 6.2, the Riot Client Launcher fails when
updating itself. This worked fine with wine 6.1 (vanilla and staging)

This wasn't much of a problem since LoL players used a lutris versions based on
wine 5.x. Starting with the last League Of Legends Client update, the CEF
upgrade requires a patched wine 6.15, so users will begin getting this error on
the next Launcher update.

The launcher throws the following error when starting the update process:
```
Update failed: Failed getting path to current executable: File path could not
be found in a mapped drive: ??\c:\Riot Games\Riot
Client\RiotClientServices.exe
```

I bisected the problem to commit bd0a3c1a59db9e75500db6df0f3598c981abf44e. For
some reason the launcher worked with the stub implementation of
GetMappedFileNameA/W, but not with a "real" one. I can confirm that reverting
the commit on 6.15 makes the update work.

Attached is a trace log of the execution (from wine staging 6.15, with the most
frequent calls removed). The interesting part should start in line 546, when
the debug message says that it will start the update, and end in line 1705,
when the update process ends. In line 1361 there is a call to
GetMappedFileNameW, which should be where the error begins.