add setresuid/setresgid functions (nonstandard)

src/unistd/setresgid.c

@@ -0,0 +1,10 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include "syscall.h"
+#include "libc.h"
+
+int setresgid(gid_t rgid, gid_t egid, gid_t sgid)
+{
+	if (libc.rsyscall) return libc.rsyscall(__NR_setresgid, rgid, egid, sgid, 0, 0, 0);
+	return syscall(SYS_setresgid, rgid, egid, sgid);
+}

src/unistd/setresuid.c

@@ -0,0 +1,10 @@
+#define _GNU_SOURCE
+#include <unistd.h>
+#include "syscall.h"
+#include "libc.h"
+
+int setresuid(uid_t ruid, uid_t euid, uid_t suid)
+{
+	if (libc.rsyscall) return libc.rsyscall(__NR_setresuid, ruid, euid, suid, 0, 0, 0);
+	return syscall(SYS_setresuid, ruid, euid, suid);
+}