Fix handling of plugin_export.h

Fixes error: definition is marked ‘dllimport’
Per LMMS#4813

plugins/carlabase/CMakeLists.txt

@@ -8,14 +8,15 @@ ENDIF()
 
 # If Carla was not provided by the system, make a dummy library instead
 if(LMMS_HAVE_WEAKCARLA)
- # Mimic the Makefile header
- FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/config.h "")
+ # Mimic the autoconf header
+ FILE(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/autoconf)
+ FILE(WRITE ${CMAKE_CURRENT_BINARY_DIR}/autoconf/config.h "")
  SET(CARLA_INCLUDE_DIRS
  ${CMAKE_CURRENT_SOURCE_DIR}/carla/source
  ${CMAKE_CURRENT_SOURCE_DIR}/carla/source/includes
  ${CMAKE_CURRENT_SOURCE_DIR}/carla/source/utils
  ${CMAKE_CURRENT_SOURCE_DIR}/carla/source/backend
- ${CMAKE_CURRENT_BINARY_DIR}
+ ${CMAKE_CURRENT_BINARY_DIR}/autoconf
  )
  INCLUDE_DIRECTORIES(${CARLA_INCLUDE_DIRS})
  ADD_LIBRARY(carla_native-plugin MODULE DummyCarla.cpp)