Make sure that all globals are internal, except for "start" functions.

src/IceELFSection.cpp

Index: src/IceELFSection.cpp
diff --git a/src/IceELFSection.cpp b/src/IceELFSection.cpp
index 3e33c99a429bc783fcb51267e5e6d5c809b141e3..37681509bb269947fe5e42831f444fcf0d90bb5c 100644
--- a/src/IceELFSection.cpp
+++ b/src/IceELFSection.cpp
@@ -116,7 +116,12 @@ void ELFSymbolTableSection::noteUndefinedSym(const IceString &Name,
   NewSymbol.Section = NullSection;
   NewSymbol.Number = ELFSym::UnknownNumber;
   bool Unique = GlobalSymbols.insert(std::make_pair(Name, NewSymbol)).second;
-  assert(Unique);
+  if (!Unique) {
+    std::string Buffer;
+    llvm::raw_string_ostream StrBuf(Buffer);
+    StrBuf << "Symbol external and defined: " << Name;
+    llvm::report_fatal_error(StrBuf.str());
+  }
   (void)Unique;
 }