switch sqlite3 to single-threaded mode

Looking at 'perf top' of osmo-msc under load shows that there's a
significant amount of time spent in terms of locking (mutex,...)
which is useless as osmo-msc is a single-threaded application.

Unfortunately libdbi doesn't provide a mechanism to perform
sqlite3_config(), so we have to do it directly here, introducing an
explicit build-time dependency (and linkage) to libsqlite3.

Related: OS#5559
Change-Id: I5bbea90d28b6d73b64b9e5124ff59304b90a8a75
diff --git a/contrib/osmo-msc.spec.in b/contrib/osmo-msc.spec.in
index 17c07b9..912804c 100644
--- a/contrib/osmo-msc.spec.in
+++ b/contrib/osmo-msc.spec.in
@@ -34,6 +34,7 @@
 %endif
 BuildRequires:  pkgconfig >= 0.20
 BuildRequires:  pkgconfig(dbi)
+BuildRequires:  pkgconfig(sqlite3)
 BuildRequires:  pkgconfig(libcrypto) >= 0.9.5
 BuildRequires:  pkgconfig(libosmo-gsup-client) >= 1.4.0
 BuildRequires:  pkgconfig(libosmo-mgcp-client) >= 1.9.0