Build System: Add variable for copying test config

If LOCAL_TEST_CONFIG is set, it will be the default test config
and ignore the local AndroidTest.xml.

BUG: 110982517
Test: vi art/tools/ahat/Android.mk
      set LOCAL_TEST_CONFIG := ahat_test.xml
      add ahat_test.xml in local
      m -j ahat;
      Then, out/host/linux-x86/testcases/ahat/ahat.config
      and ahat_test.xml should be the same.

Change-Id: I2f4ef735fca7d523bb637a18075512bdebf9826f
diff --git a/core/base_rules.mk b/core/base_rules.mk
index 770a16c..037b2cb 100644
--- a/core/base_rules.mk
+++ b/core/base_rules.mk
@@ -583,8 +583,11 @@
       $(eval n := $(or $(word 2,$(p)),$(notdir $(word 1, $(p))))) \
       $(foreach dir, $(call compatibility_suite_dirs,$(suite)), \
         $(s):$(dir)/$(n)))))
-
-  test_config := $(wildcard $(LOCAL_PATH)/AndroidTest.xml)
+  ifeq (,$(LOCAL_TEST_CONFIG))
+    test_config := $(wildcard $(LOCAL_PATH)/AndroidTest.xml)
+  else
+    test_config := $(LOCAL_PATH)/$(LOCAL_TEST_CONFIG)
+  endif
   ifeq (,$(test_config))
     ifneq (true,$(is_native))
       is_instrumentation_test := true
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index e7116a5..1c45b2b 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -266,6 +266,7 @@
 LOCAL_STRIP_MODULE:=
 LOCAL_SYSTEM_SHARED_LIBRARIES:=none
 LOCAL_TARGET_REQUIRED_MODULES:=
+LOCAL_TEST_CONFIG:=
 LOCAL_TEST_CONFIG_OPTIONS:=
 LOCAL_TEST_DATA:=
 LOCAL_TEST_MODULE_TO_PROGUARD_WITH:=