optimize/debloat raise

use __syscall rather than syscall when failure is not possible or not
to be considered.
diff --git a/src/signal/raise.c b/src/signal/raise.c
index 927fe26..b24dc74 100644
--- a/src/signal/raise.c
+++ b/src/signal/raise.c
@@ -9,8 +9,8 @@
 	int pid, tid, ret;
 	sigset_t set;
 	__syscall(SYS_rt_sigprocmask, SIG_BLOCK, SIGALL_SET, &set, _NSIG/8);
-	tid = syscall(SYS_gettid);
-	pid = syscall(SYS_getpid);
+	tid = __syscall(SYS_gettid);
+	pid = __syscall(SYS_getpid);
 	ret = syscall(SYS_tgkill, pid, tid, sig);
 	__syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, 0, _NSIG/8);
 	return ret;