rt-utils: Add gettid()

We still lack a gettid implemenation from libc.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>

src/include/rt-utils.h

@@ -22,4 +22,6 @@ int event_disable_all(void);
 const char *policy_to_string(int policy);
 uint32_t string_to_policy(const char *str);
 
+pid_t gettid(void);
+
 #endif	/* __RT_UTILS.H */

src/lib/rt-utils.c

@@ -16,6 +16,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <sys/syscall.h> /* For SYS_gettid definitions */
 #include "rt-utils.h"
 #include "rt-sched.h"
 #include "error.h"
@@ -311,3 +312,8 @@ uint32_t string_to_policy(const char *str)
 
 	return 0;
 }
+
+pid_t gettid(void)
+{
+	return syscall(SYS_gettid);
+}