Allow test to specify whether or not to auto-generate test config

Attribute `auto_gen_config` is added to test modules.
Test config will be generated if:
the attribute is not set and AndroidTest.xml doesn't exists
or
the attribute is set to true, whether or not AndroidTest.xml exists.

Test config will NOT be auto-generated if:
the attribute is not set and AndroidTest.xml exists
or
the attribute is set to false, whether or not AndroidTest.xml exists.

Bug: 141684102
Test: build test module with auto_gen_config set to true
Change-Id: I64fb003a83d8c32a967835e5f8d12fe4476043be
diff --git a/python/binary.go b/python/binary.go
index 140f07a..695fa12 100644
--- a/python/binary.go
+++ b/python/binary.go
@@ -47,6 +47,11 @@
 	// false it will act much like the normal `python` executable, but with the sources and
 	// libraries automatically included in the PYTHONPATH.
 	Autorun *bool `android:"arch_variant"`
+
+	// Flag to indicate whether or not to create test config automatically. If AndroidTest.xml
+	// doesn't exist next to the Android.bp, this attribute doesn't need to be set to true
+	// explicitly.
+	Auto_gen_config *bool
 }
 
 type binaryDecorator struct {