Linux sandbox: start adding syscall wrappers

sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc

Index: sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
index 162b3718b4a7a5b8ba5600f3a45e177371df4689..42be00b15871eec7ccb4fc082f8327bba824636e 100644
--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
@@ -17,6 +17,7 @@
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
 #include "sandbox/linux/services/linux_syscalls.h"
+#include "sandbox/linux/services/syscall_wrappers.h"
 
 #if defined(__mips__)
 // __NR_Linux, is defined in <asm/unistd.h>.
@@ -223,7 +224,7 @@ intptr_t SIGSYSSchedHandler(const struct arch_seccomp_data& args,
     case __NR_sched_setattr:
     case __NR_sched_setparam:
     case __NR_sched_setscheduler:
-      const pid_t tid = syscall(__NR_gettid);
+      const pid_t tid = sys_gettid();
       // The first argument is the pid.  If is our thread id, then replace it
       // with 0, which is equivalent and allowed by the policy.
       if (args.args[0] == static_cast<uint64_t>(tid)) {