Tests/LibWasm: Don't ignore the result of BigInt::export_data()

Prior to this commit, the test runner was ignoring the result, which
meant that values that fit in less than 128 bits were shifted to remove
the zero words (which is obviously incorrect).

Tests/LibWasm/test-wasm.cpp

@@ -285,10 +285,13 @@ JS_DEFINE_NATIVE_FUNCTION(WebAssemblyModule::wasm_invoke)
             }
 
             u128 bits = 0;
-            (void)argument.as_bigint().big_integer().unsigned_value().export_data({ bit_cast<u8*>(&bits), sizeof(bits) });
+            auto bytes = argument.as_bigint().big_integer().unsigned_value().export_data({ bit_cast<u8*>(&bits), sizeof(bits) });
             VERIFY(!argument.as_bigint().big_integer().is_negative());
 
-            arguments.append(Wasm::Value(bits));
+            if constexpr (AK::HostIsLittleEndian)
+                arguments.append(Wasm::Value(bits << (128 - bytes * 8)));
+            else
+                arguments.append(Wasm::Value(bits >> (128 - bytes * 8)));
             break;
         }
         case Wasm::ValueType::Kind::FunctionReference: