build: change default library type to static

build: change default library type to static

Now that we always build both static and shared libraries, the default
library type only applies to apps and examples. To avoid issues with
paths when doing actual development with DPDK, change the default app
build to static. This makes sure that testpmd, and any examples built as
part of a development build, are runnable without being installed.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Luca Boccassi <bluca@debian.org>