[build] Create a libbsc.a as noinst_LIBRARY, link bsc_hack and tests against it

Link the tests against the libbsc.a to avoid most of the breakage
when creating new symbols.
diff --git a/tests/sms/sms_test.c b/tests/sms/sms_test.c
index d850f3b..fe1c346 100644
--- a/tests/sms/sms_test.c
+++ b/tests/sms/sms_test.c
@@ -91,3 +91,4 @@
 
 /* stubs */
 void input_event(void) {}
+void nm_state_event(void) {}