Add GN Build Files and Custom Modifications

Signed-off-by: peizhe <472708703@qq.com>

BUILD.gn

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+# 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/ohos.gni")
+
+ohos_cargo_crate("lib") {
+  crate_name = "indexmap"
+  crate_type = "rlib"
+  crate_root = "src/lib.rs"
+
+  sources = [ "src/lib.rs" ]
+  edition = "2021"
+  cargo_pkg_version = "1.9.2"
+  cargo_pkg_name = "indexmap"
+  cargo_pkg_description =
+      "A hash table with consistent order and fast iteration."
+  deps = [ "//third_party/rust/crates/hashbrown:lib" ]
+  features = [ "std" ]
+  rustflags = [ "--cfg=has_std" ]
+}

README.OpenSource

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+[
+  {
+    "Name": "indexmap",
+    "License": "Apache License V2.0, MIT",
+    "License File": "LICENSE-APACHE, LICENSE-MIT",
+    "Version Number": "1.9.2",
+    "Owner": "xuelei3@huawei.com",
+    "Upstream URL": "https://github.com/bluss/indexmap",
+    "Description": "A hash table with consistent order and fast iteration."
+  }
+]