[ELF] IWYU <optional> NFC

GitOrigin-RevId: 23d402e5b705d98463150302a55623951284b5f2
diff --git a/ELF/DWARF.h b/ELF/DWARF.h
index e1688fe..1b9a3e3 100644
--- a/ELF/DWARF.h
+++ b/ELF/DWARF.h
@@ -13,6 +13,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/Object/ELF.h"
+#include <optional>
 
 namespace lld::elf {
 
diff --git a/ELF/InputFiles.cpp b/ELF/InputFiles.cpp
index 06a3d56..cc2c591 100644
--- a/ELF/InputFiles.cpp
+++ b/ELF/InputFiles.cpp
@@ -30,6 +30,7 @@
 #include "llvm/Support/RISCVAttributeParser.h"
 #include "llvm/Support/TarWriter.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 
 using namespace llvm;
 using namespace llvm::ELF;
diff --git a/ELF/InputSection.cpp b/ELF/InputSection.cpp
index 6e972cf..145d55d 100644
--- a/ELF/InputSection.cpp
+++ b/ELF/InputSection.cpp
@@ -22,6 +22,7 @@
 #include "llvm/Support/xxhash.h"
 #include <algorithm>
 #include <mutex>
+#include <optional>
 #include <vector>
 
 using namespace llvm;