[wasm] Fix BinOp tests for big endian systems

R=ahaas@chromium.org

Bug: v8:6600
Change-Id: I0f82f60dae124167d5dfb05b3ecb6f8b0be7c2f4
Reviewed-on: https://chromium-review.googlesource.com/995458Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52360}

test/cctest/wasm/test-run-wasm.cc

@@ -3197,11 +3197,11 @@ void BinOpOnDifferentRegisters(WasmExecutionMode execution_mode, ValueType type,
         for (ctype lhs_value : inputs) {
           for (ctype rhs_value : inputs) {
             if (lhs == rhs) lhs_value = rhs_value;
-            memory[lhs] = lhs_value;
-            memory[rhs] = rhs_value;
+            WriteLittleEndianValue<ctype>(&memory[lhs], lhs_value);
+            WriteLittleEndianValue<ctype>(&memory[rhs], rhs_value);
             int64_t expect = expect_fn(lhs_value, rhs_value);
             CHECK_EQ(0, r.Call());
-            CHECK_EQ(expect, memory[0]);
+            CHECK_EQ(expect, ReadLittleEndianValue<ctype>(&memory[0]));
           }
         }
       }