Initialize dot.

This would fix an initialized error found by msan. The error is not
showing after r298241, but it is not clear why.

llvm-svn: 298251
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 644777d..9e66151 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -430,6 +430,7 @@
   Aether = make<OutputSection>("", 0, SHF_ALLOC);
   Aether->SectionIndex = 1;
   CurOutSec = Aether;
+  Dot = 0;
 
   for (unsigned I = 0; I < Opt.Commands.size(); ++I) {
     auto Iter = Opt.Commands.begin() + I;