Windows/DirectIOFile: Don't request DELETE access for read-only Open

Aside from being unnecessary, on Windows the flag prevents two instances
of Dolphin (one instance from before 2509-371 when the flag was
introduced and the other after) from running the same ROM
simultaneously.

Attempting to do so generated the false error `"[Rom]" is an invalid
GCM/ISO file, or is not a GC/Wii ISO.` followed by `Failed to init core`
and emulation shutdown on the second instance to start the game. Fixing
the incorrect error message is a task I'm deferring to another PR.

The problem didn't happen when both instances were 2509-371 or later,
but I ran into it while bisecting an issue and it'd be nice to avoid
that problem in the future.

1 files changed, 5 insertions, 2 deletions

diff --git a/Source/Core/Common/DirectIOFile.cpp b/Source/Core/Common/DirectIOFile.cpp
index d72e98fa3b..bfe598dc48 100644
--- a/Source/Core/Common/DirectIOFile.cpp
+++ b/Source/Core/Common/DirectIOFile.cpp
@@ -86,8 +86,11 @@ bool DirectIOFile::Open(const std::string& path, AccessMode access_mode, OpenMod
   else if (access_mode == AccessMode::Write)
     desired_access = GENERIC_WRITE;
 
-  // Allow deleting and renaming through our handle.
-  desired_access |= DELETE;
+  if (access_mode != AccessMode::Read)
+  {
+    // Allow deleting and renaming through our handle.
+    desired_access |= DELETE;
+  }
 
   // All sharing is allowed to more closely match default behavior on other OSes.
   constexpr DWORD share_mode = FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE;