Add SHARED_LIB option to add_tomahawk_plugin cmake macro

Usually plugins are built as modules in cmake, but for certain plugins
we need the possibility to link against them which is only possible with
shared libs

CMakeModules/AddTomahawkPlugin.cmake

@@ -41,7 +41,7 @@ ENDMACRO(CDR)
 macro(add_tomahawk_plugin)
     parse_arguments(PLUGIN
         "SOURCES;UI;LINK_LIBRARIES;TYPE;EXPORT_MACRO;COMPILE_DEFINITIONS"
-        "NO_INSTALL"
+        "NO_INSTALL;SHARED_LIB"
         ${ARGN}
         )
     car(PLUGIN_NAME ${PLUGIN_DEFAULT_ARGS})
@@ -70,7 +70,11 @@ macro(add_tomahawk_plugin)
     endif()
 
     # add target
-    add_library(${target} MODULE ${PLUGIN_SOURCES})
+    if(NOT ${PLUGIN_SHARED_LIB})
+        add_library(${target} MODULE ${PLUGIN_SOURCES})
+    else()
+        add_library(${target} SHARED ${PLUGIN_SOURCES})
+    endif()
 
     # add qt modules
     qt5_use_modules(${target} Core Network Widgets Sql Xml DBus)