build: have a disable-static build succeed
When using configure --disable-static, no libosmogsm.a will be
created, and the tests fail to link because symbols like _a5_3 and
_a5_4 are not exported through the only remaining libosmogsm.so.
A method to overcome this is an intermediate private non-distributed
library, examples of which are present in e.g. libabc, kmod and
systemd.
With this, disable-static can now be the default and practical compile
time be halved.
diff --git a/configure.ac b/configure.ac
index c492277..9a744b1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -13,7 +13,7 @@
AC_PROG_MKDIR_P
AC_PROG_CC
AC_PROG_INSTALL
-LT_INIT([pic-only])
+LT_INIT([pic-only disable-static])
AC_CONFIG_MACRO_DIR([m4])