[Bug 48153] New: Mono's ProcessTest.Start1_FileName_Whitespace test fails in 4.20

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=48153

Bug ID: 48153
           Summary: Mono's ProcessTest.Start1_FileName_Whitespace test
                    fails in 4.20
           Product: Wine
           Version: 4.20
          Hardware: x86
                OS: Linux
            Status: NEW
          Keywords: download, regression, source, testcase
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

I've started seeing failures in the following Mono test cases:
MonoTests.System.Diagnostics.ProcessTest.Start1_FileName_Whitespace
MonoTests.System.Diagnostics.ProcessTest.Start2_FileName_Whitespace

Here's the source code for the first of those:
https://github.com/mono/mono/blob/93e46c687b0f1b3bea7ecf362a667f3bd8b59fc5/m...

Specifically, the "#6" line, which checks error codes, fails. Unfortunately, it
doesn't say what error code we got.

This worked in Wine 4.19 but fails in current master.

Bisect results and downloadable test case to follow.