Link statically to internal libraries

Link statically to internal libraries

Previously, we installed all "internal" libs as .so, because static
linking a static lib into a dynamic lib did remove the unused objects.
Use the -Wl,--no-as-needed linker flag to fix this issue, allowing us to
entirely privatize private libs.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>