openharmony 新建third_party编译不到

新建目录third_party/a_myparty

添加文件：

third_party/a_myparty/BUILD.gn

import("//build/ohos.gni")
config("a_myparty_config") {
  include_dirs = [ "." ]
}
ohos_static_library("a_myparty_static") {
    sources = [ "myparty.c" ]
    public_configs = [ ":a_myparty_config" ]
}
ohos_shared_library("a_myparty_shared") {
    deps = [ ":a_myparty_static" ]
    sources = a_myparty_sources
    subsystem_name = "hiviewdtest"
}

third_party/a_myparty/myparty.c

third_party/a_myparty/myparty.h

执行./build.sh --product-name rk3568 --build-target a_myparty_static

报错，编译不到这个目录。

[OHOS ERROR] ninja: error: unknown target 'a_myparty_static'

用的代码是openharmony3.1 release版本。

求大神解惑，在线等，谢谢！