Export cc_benchmark as NATIVE_TESTS to Make

This fixes some warnings on internal master where the compatibility
suite logic didn't look at EXECUTABLES (it was checking for
LOCAL_MODULE_CLASS == NATIVE_BENCHMARK, which doesn't exist).

Test: Compare out/soong/Android-aosp_arm64.mk
Test: Compare out/build-aosp_arm64.ninja
Change-Id: Ibe3c40e81e26f4c4cb9fd5bea1619b94181764fb
diff --git a/cc/androidmk.go b/cc/androidmk.go
index cba8782..3ce01d2 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -203,6 +203,7 @@
 
 func (benchmark *benchmarkDecorator) AndroidMk(ctx AndroidMkContext, ret *android.AndroidMkData) {
 	ctx.subAndroidMk(ret, benchmark.binaryDecorator)
+	ret.Class = "NATIVE_TESTS"
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) error {
 		if len(benchmark.Properties.Test_suites) > 0 {
 			fmt.Fprintln(w, "LOCAL_COMPATIBILITY_SUITE :=",