Fix a warning about the use of const being ignored with a cast.

llvm-svn: 211383
diff --git a/llvm/lib/Object/MachOObjectFile.cpp b/llvm/lib/Object/MachOObjectFile.cpp
index 1e105d3..a072b0f 100644
--- a/llvm/lib/Object/MachOObjectFile.cpp
+++ b/llvm/lib/Object/MachOObjectFile.cpp
@@ -1384,7 +1384,7 @@
         LibrariesShortNames.push_back(StringRef());
         continue;
       }
-      char *P = (char *)(Libraries[i]) + D.dylib.name;
+      const char *P = (const char *)(Libraries[i]) + D.dylib.name;
       StringRef Name = StringRef(P);
       StringRef Suffix;
       bool isFramework;