util/build-id: Return a pointer rather than copying the data

We're about to use the build-id as the starting point for another SHA1
hash in the Intel Vulkan driver, and returning a pointer is far more
convenient.

Reviewed-by: Chad Versace <chadversary@chromium.org>

src/intel/vulkan/anv_device.c

@@ -63,7 +63,7 @@ anv_device_get_cache_uuid(void *uuid)
    if (len < VK_UUID_SIZE)
       return false;
 
-   build_id_read(note, uuid, VK_UUID_SIZE);
+   memcpy(uuid, build_id_data(note), VK_UUID_SIZE);
    return true;
 }