[Support] Use FILE_SHARE_DELETE to fix RemoveFileOnSignal on Windows

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.

Reviewers: davide

Subscribers: llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D36337

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@310137 91177308-0d34-0410-b5e6-96231b3b80d8

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

@@ -0,0 +1,7 @@
+// 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