Force extra config file to be .config

TradeFed only supports .config file as test config.

Bug: 163344047
Test: m HelloWorldTests

Change-Id: Ib963d04fc308b9c319d5b59f50f9ca9b5b575b72
diff --git a/core/base_rules.mk b/core/base_rules.mk
index 1b41898..58be7a2 100644
--- a/core/base_rules.mk
+++ b/core/base_rules.mk
@@ -766,7 +766,7 @@
     $(foreach test_config_file, $(LOCAL_EXTRA_FULL_TEST_CONFIGS), \
       $(foreach suite, $(LOCAL_COMPATIBILITY_SUITE), \
         $(eval my_compat_dist_config_$(suite) += $(foreach dir, $(call compatibility_suite_dirs,$(suite)), \
-          $(test_config_file):$(dir)/$(notdir $(test_config_file))))))
+          $(test_config_file):$(dir)/$(basename $(notdir $(test_config_file))).config))))
   endif
 
   ifneq (,$(wildcard $(LOCAL_PATH)/DynamicConfig.xml))