Convert some assert(0) to llvm_unreachable or fold an 'if' condition into the assert.

llvm-svn: 211254
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index a98a13e..87f6ec0 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -1574,8 +1574,7 @@
     break;
 
   default:
-    assert(0 && "FIXME: sh_type value not supported!");
-    break;
+    llvm_unreachable("FIXME: sh_type value not supported!");
   }
 
   if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&