lttng-tools: do not install shared libraries in ptest package

lttng-tools: do not install shared libraries in ptest package

This was creating a race in runtime library dependency resolution
where sometimes the library was assumed to be provided by the ptest
package.

(From OE-Core rev: c4a10c0b4bc14f4bac06deed8ecb64d0303f4029)

(From OE-Core rev: 10e32463236df05458af7fb7d1ef388f380ab10c)

Signed-off-by: Alexander Kanavin <alexander.kanavin@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>