build: Respect Meson's default_library option
Distributions like to be in control of this. From a patch from James Le Cuirot.
Instead of always build both shared and static libraries for SPICE server (static is used for the tests) compile library as user requested. In case we need the static library for tests (which now can be disabled) create a static library extracting objects from shared library. This also fixes the problem that Meson installed the static library even if not requested and just used for tests.
Signed-off-by: Frediano Ziglio fziglio@redhat.com