realtime: Add configure check for GNU exp10()

Closes #13

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/testcases/realtime/configure.in b/testcases/realtime/configure.in
index 79555aa..af2cbe4 100644
--- a/testcases/realtime/configure.in
+++ b/testcases/realtime/configure.in
@@ -61,4 +61,6 @@
 fi
 REALTIME_CHECK_ROBUST_APIS
 
+LTP_CHECK_EXP10
+
 AC_OUTPUT