Adding skeleton for a rust fuzzer for legacy_blob

Test: m legacy_blob_fuzzer & adb sync data & adb shell
legacy_blob_fuzzer
The edge coverage after running for few minutes was about 15 percent.

Change-Id: I8a8a535319c6146c67980e6c31e5c85c420e40e7

keystore2/src/fuzzers/Android.bp

@@ -0,0 +1,29 @@
+// Copyright 2021, The Android Open Source Project
+//
+// 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.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+rust_fuzz {
+    name: "legacy_blob_fuzzer",
+    srcs: ["legacy_blob_fuzzer.rs"],
+    rustlibs: [
+        "libkeystore2",
+    ],
+    fuzz_config: {
+        fuzz_on_haiku_device: true,
+        fuzz_on_haiku_host: false,
+    },
+}

keystore2/src/fuzzers/legacy_blob_fuzzer.rs

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+// Copyright 2021, The Android Open Source Project
+//
+// 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.
+
+#![allow(missing_docs)]
+#![no_main]
+#[macro_use]
+extern crate libfuzzer_sys;
+use keystore2::legacy_blob::LegacyBlobLoader;
+
+fuzz_target!(|data: &[u8]| {
+    let string = data.iter().filter_map(|c| std::char::from_u32(*c as u32)).collect::<String>();
+    let _res = LegacyBlobLoader::decode_alias(&string);
+});