Use RACK_DIR in Makefile

Makefile

@@ -50,5 +50,5 @@ SOURCES += eurorack/frames/poly_lfo.cc
 
 DISTRIBUTABLES += $(wildcard LICENSE*) res
 
-
-include ../../plugin.mk
+RACK_DIR ?= ../..
+include $(RACK_DIR)/plugin.mk

src/AudibleInstruments.cpp

@@ -5,10 +5,8 @@ Plugin *plugin;
 
 void init(rack::Plugin *p) {
 	plugin = p;
-	p->slug = "AudibleInstruments";
-#ifdef VERSION
+	p->slug = TOSTRING(SLUG);
 	p->version = TOSTRING(VERSION);
-#endif
 
 	p->addModel(createModel<BraidsWidget>("Audible Instruments", "Braids", "Macro Oscillator", OSCILLATOR_TAG, WAVESHAPER_TAG));
 	p->addModel(createModel<ElementsWidget>("Audible Instruments", "Elements", "Modal Synthesizer", PHYSICAL_MODELING_TAG));