- Add logic so slave ports can build without installing base plugins.

--- src/mixer2/CMakeLists.txt.orig	2023-01-14 18:47:26 UTC
+++ src/mixer2/CMakeLists.txt
@@ -3,6 +3,7 @@ endif (${Cairo_FOUND})
 add_subdirectory (cairoblend)
 endif (${Cairo_FOUND})
 
+if (NOT BUILD_EXTRA_PLUGINS)
 add_subdirectory (addition)
 add_subdirectory (addition_alpha)
 add_subdirectory (alphaatop)
@@ -34,3 +35,4 @@ add_subdirectory (sleid0r)
 add_subdirectory (value)
 add_subdirectory (xfade0r)
 add_subdirectory (sleid0r)
+endif ()