only use getrlimit/setrlimit syscalls if they exist

riscv32 and future architectures only provide prlimit64.

src/misc/getrlimit.c

@@ -6,12 +6,13 @@
 
 int getrlimit(int resource, struct rlimit *rlim)
 {
-	unsigned long k_rlim[2];
 	int ret = syscall(SYS_prlimit64, 0, resource, 0, rlim);
 	if (!ret) {
 		FIX(rlim->rlim_cur);
 		FIX(rlim->rlim_max);
 	}
+#ifdef SYS_getrlimit
+	unsigned long k_rlim[2];
 	if (!ret || errno != ENOSYS)
 		return ret;
 	if (syscall(SYS_getrlimit, resource, k_rlim) < 0)
@@ -21,6 +22,9 @@ int getrlimit(int resource, struct rlimit *rlim)
 	FIX(rlim->rlim_cur);
 	FIX(rlim->rlim_max);
 	return 0;
+#else
+	return ret;
+#endif
 }
 
 weak_alias(getrlimit, getrlimit64);

src/misc/setrlimit.c

@@ -12,12 +12,14 @@ struct ctx {
 	int err;
 };
 
+#ifdef SYS_setrlimit
 static void do_setrlimit(void *p)
 {
 	struct ctx *c = p;
 	if (c->err>0) return;
 	c->err = -__syscall(SYS_setrlimit, c->res, c->lim);
 }
+#endif
 
 int setrlimit(int resource, const struct rlimit *rlim)
 {
@@ -29,6 +31,7 @@ int setrlimit(int resource, const struct rlimit *rlim)
 		rlim = &tmp;
 	}
 	int ret = __syscall(SYS_prlimit64, 0, resource, rlim, 0);
+#ifdef SYS_setrlimit
 	if (ret != -ENOSYS) return __syscall_ret(ret);
 
 	struct ctx c = {
@@ -42,6 +45,9 @@ int setrlimit(int resource, const struct rlimit *rlim)
 		return -1;
 	}
 	return 0;
+#else
+	return __syscall_ret(ret);
+#endif
 }
 
 weak_alias(setrlimit, setrlimit64);