Call the destructors of the MCSections.

They now contain the fragments. If we don't call the destructors the
fragments leak.

Found by an asan bot.

llvm-svn: 238161
diff --git a/llvm/lib/MC/MCContext.cpp b/llvm/lib/MC/MCContext.cpp
index 968fd26..0a453cd 100644
--- a/llvm/lib/MC/MCContext.cpp
+++ b/llvm/lib/MC/MCContext.cpp
@@ -10,6 +10,7 @@
 #include "llvm/MC/MCContext.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCDwarf.h"
 #include "llvm/MC/MCLabel.h"
@@ -54,6 +55,13 @@
 }
 
 MCContext::~MCContext() {
+  // Call the destructors so the fragments are freed
+  for (auto &I : ELFUniquingMap)
+    I.second->~MCSectionELF();
+  for (auto &I : COFFUniquingMap)
+    I.second->~MCSectionCOFF();
+  for (auto &I : MachOUniquingMap)
+    I.second->~MCSectionMachO();
 
   if (AutoReset)
     reset();