[ifs] Added missing DT_STRSZ to the .dynamic section

[haowei]

Summary

This patch adds DT_STRSZ into the dynamic section, which was absent previously. This was a bug and caused failures in other tools.

[mcgrathr]

lgtm

[phosek]

LGTM

[jhenderson]

LGTM too.

llvm/lib/InterfaceStub/ELFObjHandler.cpp

for (const IFSSymbol &Sym : Stub.Symbols) {
       DynSym.Content.add(DynStr.Content.getOffset(Sym.Name), Sym.Size, Bind,
                          convertIFSSymbolTypeToELF(Sym.Type), 0, Shndx);
     }
     DynSym.Size = DynSym.Content.getSize();
 
     // Poplulate dynamic table.
     size_t DynSymIndex = DynTab.Content.addAddr(DT_SYMTAB, 0);
     size_t DynStrIndex = DynTab.Content.addAddr(DT_STRTAB, 0);
+    DynTab.Content.addValue(DT_STRSZ, DynSym.Size);
     for (const std::string &Lib : Stub.NeededLibs)
       DynTab.Content.addValue(DT_NEEDED, DynStr.Content.getOffset(Lib));
     if (Stub.SoName)
       DynTab.Content.addValue(DT_SONAME,
                               DynStr.Content.getOffset(Stub.SoName.getValue()));
     DynTab.Size = DynTab.Content.getSize();
     // Calculate sections' addresses and offsets.
     uint64_t CurrentOffset = sizeof(Elf_Ehdr);

llvm/test/tools/llvm-ifs/write-stub.test

 # CHECK-NEXT:   Offset:
 # CHECK-NEXT:   Size:
 # CHECK-NEXT:   Link: 0
 # CHECK-NEXT:   Info: 0
 # CHECK-NEXT:   AddressAlignment: 1
 # CHECK-NEXT:   EntrySize: 0
 # CHECK-NEXT: }
 
-# CHECK:      DynamicSection [ (4 entries)
+# CHECK:      DynamicSection [ (5 entries)
 # CHECK-NEXT:   Tag                Type   Name/Value
 # CHECK-NEXT:   0x[[DYNTABZ]]0000006 SYMTAB
 # CHECK-NEXT:   0x[[DYNTABZ]]0000005 STRTAB
+# CHECK-NEXT:   0x[[DYNTABZ]]000000A STRSZ
 # CHECK-NEXT:   0x[[DYNTABZ]]0000001 NEEDED Shared library: [libc.so.6]
 # CHECK-NEXT:   0x[[DYNTABZ]]0000000 NULL
 # CHECK-NEXT: ]
 
 # CHECK:        Symbol {
 # CHECK-NEXT:     Name:
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:     Size: