[ELF] - Linkerscript: do not fail on additional semicolons in linkerscript.

Linux kernel linkerscript contains additional semicolon (last line):

.apicdrivers : AT(ADDR(.apicdrivers) - LOAD_OFFSET) {
  __apicdrivers = .;
  *(.apicdrivers);

I checked that both gold and bfd are able to parse something like:

.text : { ;;*(.text);;S = 0;; } }

Patch do the same.

Differential revision: https://reviews.llvm.org/D29276

llvm-svn: 293612