Make lldb -Werror clean for -Wstring-conversion

Also found/fixed one bug identified by this warning in
RenderScriptx86ABIFixups.cpp where a string literal was being used in an
effort to provide a name for an instruction/register, but was instead
being passed as the bool 'isVolatile' parameter.

llvm-svn: 291198
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
index 567ac88..16bb578 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDebugMap.cpp
@@ -1253,8 +1253,7 @@
       }
     }
   }
-  assert(!"this shouldn't happen");
-  return lldb::CompUnitSP();
+  llvm_unreachable("this shouldn't happen");
 }
 
 SymbolFileDWARFDebugMap::CompileUnitInfo *