Don't disable ltdl link variables when disabling internal ltdl building
Don't disable ltdl link variables when disabling internal ltdl building

We still need LIBADD, at least. Only SUBDIRS really needs to be conditionalized,
other variables are harmless (likely empty when useless).

This should fix r5222
* ltdl: don't build the embedded libltdl if plugins are enabled but the external ltdl is used

git-svn-id: 14be032f8f42541b1a281b51ae8ea69814daf20e@5223 4b44e086-7f34-40ce-a3bd-00e031736276

BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc,BlueBrain/hwloc