[Bug 46823] New: in wcmd.exe, trailing slash in "if exist SomeDir/" cause always false

https://bugs.winehq.org/show_bug.cgi?id=46823

Bug ID: 46823
           Summary: in wcmd.exe, trailing slash in "if exist SomeDir/"
                    cause always false
           Product: Wine
           Version: 4.3
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: cmd
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 63849
  --> https://bugs.winehq.org/attachment.cgi?id=63849
fix issue with instant false due to trailing slash in 'if exist SomeDir/'

if exist SomeDir/ do-smth.cmd
statement (with ending slash) always return false since
'if exist' CMD implementation start using FindFirstFileW() instead of
GetFileAttributesW() in builtins.c
Such condition appears in MS VisualStudio generated makefiles
There is special case for trailing '\', but there is no handling for '/'.
The patch proposed fixes this issue and adds corresponding tests for
if exist SomeDir/ do-smth.cmd
if exist "SomeDir/" do-smth.cmd
cases