test: port 989_ffivariadic_run to ww; retire the C carrier

Makefile

@@ -431,7 +431,7 @@ MISC_WW_TARGETS = $(MISC_WW_TESTS:%=wwtest/%)
 TOOL_WW_TESTS = test/tool/rejects_test.ww test/tool/driver_test.ww \
 	  test/tool/wwdump_test.ww test/tool/ffi_test.ww \
 	  test/tool/attest_test.ww test/tool/wwirune_test.ww \
-	  test/tool/c6soak_test.ww
+	  test/tool/c6soak_test.ww test/tool/ffivariadic_test.ww
 TOOL_WW_TARGETS = $(TOOL_WW_TESTS:%=wwtest/%)
 BOOTSTRAP_WRAPPER_SOURCES = test/wcc/950_selfcheck.c \
 	  test/wcc/991_w6a_ww.c \
@@ -464,18 +464,19 @@ $(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.
+# test/tool/ffivariadic_test.ww links a C callee archive it reaches
+# via testenv.repo() + /out/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
+wwtest/test/tool/ffivariadic_test.ww: $(OUT)/ffivariadic/libffifix.a
 
 # Native library tests execute their source owner directly.  The retired C
 # launchers added no assertion beyond this exit status.