[clang] [clang][deps] Add `-o` flag to specify output path (PR #88767)

[Ben Langmuir via cfe-commits]

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@@ -864,8 +873,24 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
       });
 
   SharedStream Errs(llvm::errs());
-  // Print out the dependency results to STDOUT by default.
-  SharedStream DependencyOS(llvm::outs());
+
+  std::optional<llvm::raw_fd_ostream> FileOS;
+  llvm::raw_ostream &ThreadUnsafeDependencyOS = [&]() -> llvm::raw_ostream & {
+    if (OutputFileName == "-")
+      return llvm::outs();
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benlangmuir wrote:

I don't feel strongly about whether you should change this code or not -- maybe it's clearer the way it is? -- but `raw_fd_ostream("-", EC)` is going to be the same as `outs()` anyway.

https://github.com/llvm/llvm-project/pull/88767