[ELF] - Eliminate dead code. NFC.

Code is dead because caller of the isDuplicateArmExidxSex
(https://github.com/llvm-mirror/lld/blob/master/ELF/Writer.cpp#L1446)

explicitly does not pass sentinel. So no reason to check it.

llvm-svn: 336891

Author: George Rimar

lld/ELF/Writer.cpp

@@ -1388,10 +1388,6 @@ static bool isDuplicateArmExidxSec(InputSection *Prev, InputSection *Cur) {
   // consecutive identical entries are rare and the effort to check that they
   // are identical is high.
 
-  if (isa<SyntheticSection>(Cur))
-    // Exidx sentinel section has implicit EXIDX_CANTUNWIND;
-    return PrevEntry.Unwind == 0x1;
-
   ArrayRef<const ExidxEntry> Entries(
       reinterpret_cast<const ExidxEntry *>(Cur->Data.data()),
       Cur->getSize() / sizeof(ExidxEntry));