Set the constant pool size to 0 on architectures that do not use it.

src/arm64/assembler-arm64.cc

Index: src/arm64/assembler-arm64.cc
diff --git a/src/arm64/assembler-arm64.cc b/src/arm64/assembler-arm64.cc
index d981f635ba0f4ba3ad9578f271e98553712351cd..510bf79b8277b0e2cac1b3b0535fd6ad87551e70 100644
--- a/src/arm64/assembler-arm64.cc
+++ b/src/arm64/assembler-arm64.cc
@@ -589,6 +589,7 @@ void Assembler::GetCode(CodeDesc* desc) {
         static_cast<int>((reinterpret_cast<byte*>(buffer_) + buffer_size_) -
                          reloc_info_writer.pos());
     desc->origin = this;
+    desc->constant_pool_size = 0;
   }
 }