libs: Don't allow static libraries to be built

Static libraries have no namespacing, so our "private" symbols become global. This results in functions like os_create_anonymous_file() crashing into functions of the same name in multiple projects.

Since our test suite fails for static builds already, it's probably a clear indication that they're not well tested - so let's just force everything to be shared instead of trying to fix up static support.

Signed-off-by: Derek Foreman derek.foreman@collabora.com