Simplify use of config files

Since the exposed API won't support config files:
- Don't use a config file for the demo app.
- Don't use config files for tests that don't need one.

Also, in preparation for removing command line argument support
entirely, remove all arguments from config files. Where we were using
arguments to specify behavior, use different binaries instead.

Tweak: Improve error reporting in the benchmark after I got a (sadly
non-reproducible) failure.

Bug: 250876593
Bug: 243513572
Test: atest MicrodroidTests MicrodroidHostTestCases
Test: atest MicrodroidBenchmarkApp
Test: manual - install & run demo app
Change-Id: I4332b2340bf2e18cdaee5acd9ef3277766b1c0b5
diff --git a/tests/benchmark/src/native/idlebinary.cpp b/tests/benchmark/src/native/idlebinary.cpp
new file mode 100644
index 0000000..a74e7bf
--- /dev/null
+++ b/tests/benchmark/src/native/idlebinary.cpp
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+#include <unistd.h>
+
+extern "C" int android_native_main(int /* argc */, char* /* argv */[]) {
+    // do nothing; just leave it alive. good night.
+    for (;;) {
+        sleep(1000);
+    }
+}