[lld][macho] Fix implicit dependency on DenseMap.h include

RKSimon · RKSimon · commit 0847cfa334d0 · 2020-04-27T14:05:29.000+01:00
It was depending on CachedHashString.h providing the include.
diff --git a/lld/MachO/SymbolTable.h b/lld/MachO/SymbolTable.h
@@ -11,6 +11,7 @@
 
 #include "lld/Common/LLVM.h"
 #include "llvm/ADT/CachedHashString.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/Object/Archive.h"
 
 namespace lld {
