Fix a gcc warning.

Thanks to Filipe Cabecinhas for the report.

llvm-svn: 220361
diff --git a/llvm/tools/gold/gold-plugin.cpp b/llvm/tools/gold/gold-plugin.cpp
index bb0488a..f65cdf2 100644
--- a/llvm/tools/gold/gold-plugin.cpp
+++ b/llvm/tools/gold/gold-plugin.cpp
@@ -278,7 +278,7 @@
       message(LDPL_ERROR, "Failed to get a view of %s", file->name);
       return LDPS_ERR;
     }
-    BufferRef = MemoryBufferRef(StringRef((char *)view, file->filesize), "");
+    BufferRef = MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
   } else {
     int64_t offset = 0;
     // Gold has found what might be IR part-way inside of a file, such as