vulkan: Add #ifdef hack to vk_android_native_buffer.h

This patch consolidates many potential `#ifdef ANDROID` messes
throughout src/vulkan and src/intel/vulkan into a simple, localized
hack. The hack is an `#ifdef ANDROID` in vk_android_native_buffer.h
that, on non-Android platorms, avoids including the Android platform
headers and typedefs any Android-specific types to void*.

This hack doesn't remove *all* the `#ifdef ANDROID`s in upcoming
patches, but it does remove a lot.

I first tried implementing VK_ANDROID_native_buffer without this hack,
but eventually gave up when the yak shaving became too much.

Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

include/vulkan/vk_android_native_buffer.h

@@ -17,8 +17,13 @@
 #ifndef __VK_ANDROID_NATIVE_BUFFER_H__
 #define __VK_ANDROID_NATIVE_BUFFER_H__
 
+/* MESA: A hack to avoid #ifdefs in driver code. */
+#ifdef ANDROID
 #include <system/window.h>
 #include <vulkan/vulkan.h>
+#else
+typedef void *buffer_handle_t;
+#endif
 
 #ifdef __cplusplus
 extern "C" {