Fix build with zynaddsubfx dependencies installed

Signed-off-by: falkTX <falktx@falktx.com>

carla

@@ -1 +1 @@
-Subproject commit c24dcfd3c1ac8793c59c8ff0b7310e4c276c5368
+Subproject commit 8c8efd2b1eeec5cf80cb6cd6739cbc70cbbc9bee

src/Makefile.cardinal.mk

@@ -16,6 +16,10 @@ SYSDEPS ?= false
 # --------------------------------------------------------------
 # Carla stuff
 
+ifneq ($(DEBUG),true)
+EXTERNAL_PLUGINS = true
+endif
+
 CWD = ../../carla/source
 include $(CWD)/Makefile.deps.mk