LoongArch: Sink #include llvm/BinaryFormat/ELF.h from LoongArchMCExpr.h. NFC

Remove a fishy `#undef LoongArch` and an unneeded user-provided dtor.

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp

diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
index eaf56f6..23d936b 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
@@ -12,6 +12,7 @@
 
 #include "LoongArchAsmBackend.h"
 #include "LoongArchFixupKinds.h"
+#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
@@ -27,6 +28,12 @@
 
 using namespace llvm;
 
+LoongArchAsmBackend::LoongArchAsmBackend(const MCSubtargetInfo &STI,
+                                         uint8_t OSABI, bool Is64Bit,
+                                         const MCTargetOptions &Options)
+    : MCAsmBackend(llvm::endianness::little, ELF::R_LARCH_RELAX), STI(STI),
+      OSABI(OSABI), Is64Bit(Is64Bit), TargetOptions(Options) {}
+
 std::optional<MCFixupKind>
 LoongArchAsmBackend::getFixupKind(StringRef Name) const {
   if (STI.getTargetTriple().isOSBinFormatELF()) {

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.h

diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.h b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.h
index ec78f34..94518ac 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.h
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.h
@@ -33,10 +33,7 @@
 
 public:
   LoongArchAsmBackend(const MCSubtargetInfo &STI, uint8_t OSABI, bool Is64Bit,
-                      const MCTargetOptions &Options)
-      : MCAsmBackend(llvm::endianness::little, ELF::R_LARCH_RELAX), STI(STI),
-        OSABI(OSABI), Is64Bit(Is64Bit), TargetOptions(Options) {}
-  ~LoongArchAsmBackend() override {}
+                      const MCTargetOptions &Options);
 
   bool handleAddSubRelocations(const MCAssembler &Asm, const MCFragment &F,
                                const MCFixup &Fixup, const MCValue &Target,

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchFixupKinds.h

diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchFixupKinds.h b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchFixupKinds.h
index 515eab0..d4c2323 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchFixupKinds.h
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchFixupKinds.h
@@ -9,11 +9,8 @@
 #ifndef LLVM_LIB_TARGET_LOONGARCH_MCTARGETDESC_LOONGARCHFIXUPKINDS_H
 #define LLVM_LIB_TARGET_LOONGARCH_MCTARGETDESC_LOONGARCHFIXUPKINDS_H
 
-#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCFixup.h"
 
-#undef LoongArch
-
 namespace llvm {
 namespace LoongArch {
 //

llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp

diff --git a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
index b72d84e..fa965d1 100644
--- a/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
+++ b/llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchMCCodeEmitter.cpp
@@ -13,6 +13,7 @@
 #include "LoongArchFixupKinds.h"
 #include "MCTargetDesc/LoongArchMCExpr.h"
 #include "MCTargetDesc/LoongArchMCTargetDesc.h"
+#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/MC/MCCodeEmitter.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCInstBuilder.h"