Add a missing dependency to fix build.

llvm-svn: 351458
diff --git a/llvm/tools/llvm-readobj/CMakeLists.txt b/llvm/tools/llvm-readobj/CMakeLists.txt
index b0550f3..389e348 100644
--- a/llvm/tools/llvm-readobj/CMakeLists.txt
+++ b/llvm/tools/llvm-readobj/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(LLVM_LINK_COMPONENTS
   DebugInfoCodeView
   DebugInfoDWARF
+  Demangle
   Object
   BinaryFormat
   Support