Bug#960250: guitarix FTBFS with lv2-dev 1.18.0-1

[Adrian Bunk <bunk@debian.org>]

Source: guitarix
Version: 0.39.0+dfsg1-2
Severity: serious
Tags: ftbfs

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/guitarix.html

...
../src/LV2/gxautowah.lv2/gxautowah_gui.cpp:194:21: error: invalid conversion from 'void* (*)(const _LV2UI_Descriptor*, const char*, const char*, LV2UI_Write_Function, LV2UI_Controller, void**, const LV2_Feature* const*)' {aka 'void* (*)(const _LV2UI_Descriptor*, const char*, const char*, void (*)(void*, unsigned int, unsigned int, unsigned int, const void*), void*, void**, const LV2_Feature* const*)'} to 'void* (*)(const LV2UI_Descriptor*, const char*, const char*, LV2UI_Write_Function, LV2UI_Controller, void**, const LV2_Feature* const*)' {aka 'void* (*)(const LV2UI_Descriptor*, const char*, const char*, void (*)(void*, unsigned int, unsigned int, unsigned int, const void*), void*, void**, const LV2_Feature* const*)'} [-fpermissive]
  194 |   {GXPLUGIN_UI_URI, instantiate, cleanup, port_event, NULL}
      |                     ^~~~~~~~~~~
      |                     |
      |                     void* (*)(const _LV2UI_Descriptor*, const char*, const char*, LV2UI_Write_Function, LV2UI_Controller, void**, const LV2_Feature* const*) {aka void* (*)(const _LV2UI_Descriptor*, const char*, const char*, void (*)(void*, unsigned int, unsigned int, unsigned int, const void*), void*, void**, const LV2_Feature* const*)}
...