Fix embedded (arm-none-eabi) builds

Due to OS#3360, build testing for arm-none-eabi was unfortunately
skipped for a long time.  This is a number of fixes that make the
compile test pass again.

Related: OS#3360
Change-Id: I88e3c8e1a8786ca2a6a023b0d27c74be200a8588
diff --git a/src/timer_clockgettime.c b/src/timer_clockgettime.c
index 8d9760c..7b17fd1 100644
--- a/src/timer_clockgettime.c
+++ b/src/timer_clockgettime.c
@@ -44,6 +44,9 @@
 /*! \file timer_clockgettime.c
  */
 
+#include "config.h"
+#ifdef HAVE_CLOCK_GETTIME
+
 #include <stdlib.h>
 #include <stdbool.h>
 #include <sys/time.h>
@@ -135,4 +138,6 @@
 		timespecadd(&c->time, &val, &c->time);
 }
 
+#endif /* HAVE_CLOCK_GETTIME */
+
 /*! @} */