Add rust_test and rust_test_host.

* Rust tests are like binary files compiled with --test.
  New test.go follows binary.go code patterns and reuses
  some code in binary.go.
* Generate one test per source file as testPerSrc in cc/test.go.
  The "all tests" variation feature of cc/test.go is not copied yet.
  Fix some Stem and SubName settings to make testPerSrc work.
* Move cc.CheckDuplicate to android.CheckDuplicate,
  which is now shared by cc and rust.
* Refactor tests in binary_test.go and add new test_test.go.

Bug: 140938178
Test: mm in rust projects, added rust_test and rust_test_host
Change-Id: Ia6fec8b4cf2572fd352ab1938a1f3c7b5cca2212

rust/test_test.go

@@ -0,0 +1,43 @@
+// Copyright 2019 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 rust
+
+import (
+	"strings"
+	"testing"
+)
+
+// Check if rust_test_host accepts multiple source files and applies --test flag.
+func TestRustTest(t *testing.T) {
+	ctx := testRust(t, `
+		rust_test_host {
+			name: "my_test",
+			srcs: ["foo.rs", "src/bar.rs"],
+			relative_install_path: "rust/my-test",
+		}`)
+
+	for _, name := range []string{"foo", "bar"} {
+		testingModule := ctx.ModuleForTests("my_test", "linux_glibc_x86_64_"+name)
+		testingBuildParams := testingModule.Output(name)
+		rustcFlags := testingBuildParams.Args["rustcFlags"]
+		if !strings.Contains(rustcFlags, "--test") {
+			t.Errorf("%v missing --test flag, rustcFlags: %#v", name, rustcFlags)
+		}
+		outPath := "/my_test/linux_glibc_x86_64_" + name + "/" + name
+		if !strings.Contains(testingBuildParams.Output.String(), outPath) {
+			t.Errorf("wrong output: %v  expect: %v", testingBuildParams.Output, outPath)
+		}
+	}
+}