some ugly hacks to make wip-lttng build on wheezy

We avoid compiling in lttng on select old platforms (wheezy, precise, el6).
However, debian doesn't let you have conditoinals on the debian/control file
for the BuildDepends.  Normally this is okay because the packages exist on
those distros.  But wheezy doesn't have it...
this needs quotes, it is not safe to operate on paths without quotes