make: restore the dropped ffivariadic callee-archive rule

Makefile

@@ -387,6 +387,19 @@ $(BIN)/test_400_w6c: test/wcc/400_w6c.c \
 $(BIN)/test_%: test/wcc/%.c test/wcc/wwtestpkg.h $(LIB)/libwcc.a | $(BIN)
 	$(CC) $(CFLAGS) $(INCS) -o $@ $< $(LIB)/libwcc.a
 
+# 989_ffivariadic depends on a C callee archive the harness finds via
+# $(BIN)/../ffivariadic. The fixture is built self-contained (zero
+# relocs + undef syms) so w6l links it with no libc; flags are fixed,
+# NOT $(CFLAGS), to keep that property. The rule was dropped in the
+# test-graph rewrite (228a632a) and a stale out/ tree masked it.
+$(OUT)/ffivariadic/libffifix.a: test/wcc/data/ffivariadic/fixture.c
+	@mkdir -p $(OUT)/ffivariadic
+	$(CC) -O1 -fno-stack-protector -fno-asynchronous-unwind-tables \
+		-fcf-protection=none -c -o $(OUT)/ffivariadic/fixture.o $<
+	$(AR) rcs $@ $(OUT)/ffivariadic/fixture.o
+
+$(BIN)/test_989_ffivariadic_run: $(OUT)/ffivariadic/libffifix.a
+
 # Native library tests execute their source owner directly.  The retired C
 # launchers added no assertion beyond this exit status.
 LIBRARY_TESTS = lib/errors/errno_test.ww lib/ascii/ascii_test.ww \