[AsmPrinter] Destroy allocated DIEAbbrevs on teardown.

DIEAbbrev contains a SmallVector that can leak for overly large abbrevs. They
used to be owned by the DIE, but after the recent refactoring DWARFFile
allocates its own abbrevs.

Leak found by asan.

llvm-svn: 238418

llvm/lib/CodeGen/AsmPrinter/DwarfFile.cpp

@@ -20,7 +20,10 @@ namespace llvm {
 DwarfFile::DwarfFile(AsmPrinter *AP, StringRef Pref, BumpPtrAllocator &DA)
     : Asm(AP), StrPool(DA, *Asm, Pref) {}
 
-DwarfFile::~DwarfFile() {}
+DwarfFile::~DwarfFile() {
+  for (DIEAbbrev *Abbrev : Abbreviations)
+    Abbrev->~DIEAbbrev();
+}
 
 // Define a unique number for the abbreviation.
 //