[ELF] - Linkerscript: set correct dynamic tag entries values when LS is used.

Previously DT_PREINIT_ARRAYSZ, DT_INIT_ARRAYSZ and DT_FINI_ARRAYSZ
were set to zero when lincerscript was used becase sections sizes are
calculated later that were taken.

Patch delays values calculation for these entries. Testcase is provided.

Differential revision: https://reviews.llvm.org/D23663

llvm-svn: 279258