build: fix build with single plugins

We need to quote arguments with [] so that lists are not expanded as
different arguments.

Fixes 65560dd885

m4/mm-enable-plugin.m4

@@ -44,14 +44,14 @@ dnl Usage:
 dnl  MM_ENABLE_PLUGIN([NAME],[WITH_SHARED_NAME_1,WITH_SHARED_NAME_2,...])
 AC_DEFUN([MM_ENABLE_PLUGIN],
 [dnl
-MM_ENABLE_PLUGIN_FULL($1,$enable_all_plugins,$2)
+MM_ENABLE_PLUGIN_FULL([$1],[$enable_all_plugins],[$2])
 ])
 
 dnl Usage:
 dnl  MM_ENABLE_PLUGIN_DISABLED([NAME],[WITH_SHARED_NAME_1,WITH_SHARED_NAME_2,...])
 AC_DEFUN([MM_ENABLE_PLUGIN_DISABLED],
 [dnl
-MM_ENABLE_PLUGIN_FULL($1,"no",$2)
+MM_ENABLE_PLUGIN_FULL([$1],["no"],[$2])
 ])
 
 dnl Usage: