[Bug 50613] New: several Wine Mono tests fail to load a referenced assembly on x86_64

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=50613

Bug ID: 50613
           Summary: several Wine Mono tests fail to load a referenced
                    assembly on x86_64
           Product: Wine
           Version: 6.1
          Hardware: x86-64
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ntdll
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

When running the x86_64.bug-324535 testcase from Wine Mono, it fails with this
exception:

Unhandled Exception:
System.IO.FileNotFoundException: Could not load file or assembly
'bug-324535-il, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one
of its dependencies.
File name: 'bug-324535-il, Version=0.0.0.0, Culture=neutral,
PublicKeyToken=null'
[ERROR] FATAL UNHANDLED EXCEPTION: System.IO.FileNotFoundException: Could not
load file or assembly 'bug-324535-il, Version=0.0.0.0, Culture=neutral,
PublicKeyToken=null' or one of its dependencies.
Test failed(1): x86_64.bug-324535
0 tests passed, 1 tests failed

This can easily be checked by downloading the wine-mono tests zip file and
running:
$ wine run-tests.exe x86_64.bug-324535

Other testcases fail in a similar way, but only when run in a 64-bit process.
For example, x86.bug-324535 passes.

Bisect result:

7203ad0ecd06b451116fcfe3b08e4d620e853bd5 is the first bad commit
commit 7203ad0ecd06b451116fcfe3b08e4d620e853bd5
Author: Alexandre Julliard 
Date:   Thu Jan 21 12:31:34 2021 +0100

ntdll: Load the COR header directly from the file handle.