selfhost: port append + spread — N_SPREAD parser + rt_ensure builtin

test/wcc/994_w6c_ww.c

@@ -159,6 +159,25 @@ main(void)
 		  "  return -1;\n"
 		  "};\n"
 		  "fn main() i32 = { return classify(2); };" },
+		{ "append",
+		  "use os;\n"
+		  "fn main() i32 = {\n"
+		  "  let s: []u8;\n"
+		  "  s.ptr = nil; s.len = 0; s.cap = 0;\n"
+		  "  append(s, 65u8, 66u8, 67u8);\n"
+		  "  return s.len: i32;\n"
+		  "};" },
+		{ "append_spread",
+		  "use os;\n"
+		  "fn main() i32 = {\n"
+		  "  let src: []i64;\n"
+		  "  src.ptr = nil; src.len = 0; src.cap = 0;\n"
+		  "  append(src, 10i64, 20i64);\n"
+		  "  let dst: []i64;\n"
+		  "  dst.ptr = nil; dst.len = 0; dst.cap = 0;\n"
+		  "  append(dst, src...);\n"
+		  "  return dst.len: i32;\n"
+		  "};" },
 		{ NULL, NULL },
 	};