[PATCH] [lld][ELF][Writer] Add dynamic symbol table.

[Michael Spencer]

  Actually, this is wrong.

      [Nr] Name              Type             Address           Offset
           Size              EntSize          Flags  Link  Info  Align
      [ 2] .dynsym           DYNSYM           0000000000402000  00002000
           0000000000000048  0000000000000018   A       0     0     8
      [ 3] .dynstr           STRTAB           0000000000402048  00002048
           0000000000000009  0000000000000000   A       0     0     1

  Link it not getting set properly.

  The problem is that mergeSimiliarSections gets the _link value before finalize is called. Thus the _link member has not been set.

http://llvm-reviews.chandlerc.com/D442