Use a nonzero initial size with llvm::SmallSet.

(cherry picked from commit f1a87b6)

Author: maleadt

src/jitlayers.h

@@ -241,7 +241,7 @@ struct jl_codegen_params_t {
     SmallVector<cfunc_decl_t,0> cfuncs;
     std::map<void*, GlobalVariable*> global_targets;
     jl_array_t *temporary_roots = nullptr;
-    SmallSet<jl_value_t *, 0> temporary_roots_set;
+    SmallSet<jl_value_t *, 8> temporary_roots_set;
     std::map<std::tuple<jl_code_instance_t*,bool>, GlobalVariable*> external_fns;
     std::map<jl_datatype_t*, DIType*> ditypes;
     std::map<jl_datatype_t*, Type*> llvmtypes;