wasi: fix clean target in test/wasi/Makefile

PR-URL: #59576
Refs: https://www.gnu.org/software/make/manual/make.html#Cleanup
Refs: https://www.gnu.org/software/make/manual/make.html#Parallel-Disable
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: aduh95

test/wasi/Makefile

@@ -12,5 +12,7 @@ wasm/pthread.wasm : c/pthread.c
 wasm/%.wasm : c/%.c
 	$(CC) $< $(CFLAGS) --target=$(TARGET) --sysroot=$(SYSROOT) -s -o $@
 
-.PHONY clean:
+.PHONY: clean
+.NOTPARALLEL: clean
+clean:
 	rm -f $(OBJ)