[Support] Use FILE_SHARE_DELETE to fix RemoveFileOnSignal on Windows

[rnk]

Summary

Tools like clang that use RemoveFileOnSignal on their output files
weren't actually able to clean up their outputs before this change. Now
the call to llvm::sys::fs::remove succeeds and the temporary file is
deleted. This is a stop-gap to fix clang before implementing the
solution outlined in PR34070.

[davide]

LGTM as a stopgap solution (and realistically, we won't have the new library today).

cfe/trunk/test/Frontend/remove-file-on-signal.c

+// RUN: rm -rf %t && mkdir -p %t && cd %t
+// RUN: not --crash %clang_cc1 %s -emit-llvm -o foo.ll
+// RUN: ls . | FileCheck %s --allow-empty
+// CHECK-NOT: foo.ll
+
+#pragma clang __debug crash
+FOO

llvm/trunk/lib/Support/Windows/Path.inc

else if (Flags & F_Append)
     CreationDisposition = OPEN_ALWAYS;
   else
     CreationDisposition = CREATE_ALWAYS;
 
   DWORD Access = GENERIC_WRITE;
   if (Flags & F_RW)
     Access |= GENERIC_READ;
 
-  HANDLE H = ::CreateFileW(PathUTF16.begin(), Access,
-                           FILE_SHARE_READ | FILE_SHARE_WRITE, NULL,
-                           CreationDisposition, FILE_ATTRIBUTE_NORMAL, NULL);
+  HANDLE H =
+      ::CreateFileW(PathUTF16.begin(), Access,
+                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                    NULL, CreationDisposition, FILE_ATTRIBUTE_NORMAL, NULL);
 
   if (H == INVALID_HANDLE_VALUE) {
     DWORD LastError = ::GetLastError();
     std::error_code EC = mapWindowsError(LastError);
     // Provide a better error message when trying to open directories.
     // This only runs if we failed to open the file, so there is probably
     // no performances issues.
     if (LastError != ERROR_ACCESS_DENIED)