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
diff --git a/rust/binary_test.go b/rust/binary_test.go
index cd41fcf..ab2dae1 100644
--- a/rust/binary_test.go
+++ b/rust/binary_test.go
@@ -36,11 +36,20 @@
 	fizzBuzz := ctx.ModuleForTests("fizz-buzz", "linux_glibc_x86_64").Output("fizz-buzz")
 	fizzBuzzDynamic := ctx.ModuleForTests("fizz-buzz-dynamic", "linux_glibc_x86_64").Output("fizz-buzz-dynamic")
 
-	if !strings.Contains(fizzBuzzDynamic.Args["rustcFlags"], "prefer-dynamic") {
-		t.Errorf("missing prefer-dynamic flag, rustcFlags: %#v", fizzBuzzDynamic.Args["rustcFlags"])
+	// Do not compile binary modules with the --test flag.
+	flags := fizzBuzzDynamic.Args["rustcFlags"]
+	if strings.Contains(flags, "--test") {
+		t.Errorf("extra --test flag, rustcFlags: %#v", flags)
+	}
+	if !strings.Contains(flags, "prefer-dynamic") {
+		t.Errorf("missing prefer-dynamic flag, rustcFlags: %#v", flags)
 	}
 
-	if strings.Contains(fizzBuzz.Args["rustcFlags"], "prefer-dynamic") {
-		t.Errorf("unexpected prefer-dynamic flag, rustcFlags: %#v", fizzBuzz.Args["rustcFlags"])
+	flags = fizzBuzz.Args["rustcFlags"]
+	if strings.Contains(flags, "--test") {
+		t.Errorf("extra --test flag, rustcFlags: %#v", flags)
+	}
+	if strings.Contains(flags, "prefer-dynamic") {
+		t.Errorf("unexpected prefer-dynamic flag, rustcFlags: %#v", flags)
 	}
 }