timer: Introduce osmo_clock_gettime to override clock_gettime

Change-Id: I5bebc6e01fc9d238065bc2517058f0ba85620349
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 0ec852c..15a89b6 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -240,6 +240,12 @@
 AT_CHECK([$abs_top_builddir/tests/timer/timer_test], [0], [expout], [ignore])
 AT_CLEANUP
 
+AT_SETUP([clk_override])
+AT_KEYWORDS([clk_override])
+cat $abs_srcdir/timer/clk_override_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/timer/clk_override_test], [0], [expout], [ignore])
+AT_CLEANUP
+
 AT_SETUP([tlv])
 AT_KEYWORDS([tlv])
 cat $abs_srcdir/tlv/tlv_test.ok > expout