[llvm][object] Expose writeArchiveToStream (#98254)

This internal helper is a useful API to have, when one wants to write an
archive directly to some other preallocated stream.

Author: Jeff Niu

llvm/include/llvm/Object/ArchiveWriter.h

@@ -48,6 +48,13 @@ enum class SymtabWritingMode {
   BigArchive64  // Only write the 64-bit symbol table.
 };
 
+// Write an archive directly to an output stream.
+Error writeArchiveToStream(raw_ostream &Out,
+                           ArrayRef<NewArchiveMember> NewMembers,
+                           SymtabWritingMode WriteSymtab,
+                           object::Archive::Kind Kind, bool Deterministic,
+                           bool Thin, std::optional<bool> IsEC = std::nullopt);
+
 Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
                    SymtabWritingMode WriteSymtab, object::Archive::Kind Kind,
                    bool Deterministic, bool Thin,

llvm/lib/Object/ArchiveWriter.cpp

@@ -997,10 +997,11 @@ Expected<std::string> computeArchiveRelativePath(StringRef From, StringRef To) {
   return std::string(Relative);
 }
 
-static Error
-writeArchiveToStream(raw_ostream &Out, ArrayRef<NewArchiveMember> NewMembers,
-                     SymtabWritingMode WriteSymtab, object::Archive::Kind Kind,
-                     bool Deterministic, bool Thin, std::optional<bool> IsEC) {
+Error writeArchiveToStream(raw_ostream &Out,
+                           ArrayRef<NewArchiveMember> NewMembers,
+                           SymtabWritingMode WriteSymtab,
+                           object::Archive::Kind Kind, bool Deterministic,
+                           bool Thin, std::optional<bool> IsEC) {
   assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
 
   SmallString<0> SymNamesBuf;