bp2build support for python_test(_host)

There was a request for using b with python tests. bp2build python
tests exactly the same way as python binaries so that they can be
used with `b`.

Bug: None
Test: go test
Change-Id: Id68a6a73572745a4885b3e5bb1b8452e36baa982
diff --git a/python/binary.go b/python/binary.go
index 75135f3..a5db2f6 100644
--- a/python/binary.go
+++ b/python/binary.go
@@ -37,7 +37,7 @@
 	// this file must also be listed in srcs.
 	// If left unspecified, module name is used instead.
 	// If name doesn’t match any filename in srcs, main must be specified.
-	Main *string `android:"arch_variant"`
+	Main *string
 
 	// set the name of the output binary.
 	Stem *string `android:"arch_variant"`