[wasm] Support undefined indirect table entries, behind a flag.

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index c23f08f6fdaa3241e11bfb76bb1697bf859d407d..9021e11bb89308d96533a8033facc6ee5db6981b 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -512,6 +512,9 @@ DEFINE_BOOL(print_wasm_code_size, false,
 DEFINE_INT(typed_array_max_size_in_heap, 64,
            "threshold for in-heap typed array")
 
+DEFINE_BOOL(wasm_jit_prototype, false,
+            "enable experimental wasm runtime dynamic code generation")
+
 // Profiler flags.
 DEFINE_INT(frame_count, 1, "number of stack frames inspected by the profiler")
 // 0x1800 fits in the immediate field of an ARM instruction.