tests: Fix Android build

Move unused variable within the #ifdef block that uses it.

Change-Id: Ia3a968c1f1f237b1e244493319f15cab8cda293f
diff --git a/tests/layer_validation_tests.cpp b/tests/layer_validation_tests.cpp
index 8689374..040560f 100644
--- a/tests/layer_validation_tests.cpp
+++ b/tests/layer_validation_tests.cpp
@@ -1649,9 +1649,9 @@
 
 TEST_F(VkWsiEnabledLayerTest, TestEnabledWsi) {
 
+#if defined(VK_USE_PLATFORM_XCB_KHR)
     VkSurfaceKHR surface = VK_NULL_HANDLE;
 
-#if defined(VK_USE_PLATFORM_XCB_KHR)
     VkResult err;
     bool pass;
     VkSwapchainKHR swapchain = VK_NULL_HANDLE;