Add BUILD.gn for OH build

Issue:https://gitee.com/openharmony/build/issues/I6UFTP

Signed-off-by: haotuo <haotuo@huawei.com>

BUILD.gn

@@ -0,0 +1,32 @@
+# Copyright (c) 2023 Huawei Device Co., Ltd.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//build/templates/rust/ohos_cargo_crate.gni")
+
+ohos_cargo_crate("lib") {
+    crate_name = "memoffset"
+    crate_type = "rlib"
+    crate_root = "src/lib.rs"
+
+    sources = ["src/lib.rs"]
+    edition = "2015"
+    cargo_pkg_version = "0.7.1"
+    cargo_pkg_authors = "Gilad Naaman <gilad.naaman@gmail.com>"
+    cargo_pkg_name = "memoffset"
+    cargo_pkg_description = "offset_of functionality for Rust structs."
+    build_deps = ["//third_party/rust/crates/autocfg:lib"]
+    features = ["default"]
+    build_root = "build.rs"
+    build_sources = ["build.rs"]
+    build_script_outputs = ["probe0.ll"]
+}