build/make: auto generate Test config file for Google Benchmark Test

BUG: 74844131
Test: cd bionic/; mm (auto generating the test config in out/)
      atest bionic-benchmarks (full testing in atest)
Change-Id: I0497eed876640893d0b82d4cde384d3608cf4875
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 62549d9..d0fe048 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -163,6 +163,7 @@
 LOCAL_MODULE_UNSUPPORTED_TARGET_ARCH:=
 LOCAL_MODULE_UNSUPPORTED_TARGET_ARCH_WARN:=
 LOCAL_MULTILIB:=
+LOCAL_NATIVE_BENCHMARK:=
 LOCAL_NDK_STL_VARIANT:=
 LOCAL_NDK_VERSION:=current
 LOCAL_NO_CRT:=