Allow .o files as srcs.

Test: m nothing
Test: TreeHugger
Bug: 134581881
Bug: 137267623

Change-Id: I26307dd1129e58878f0468da3b61c53f074bd674
diff --git a/cc/testing.go b/cc/testing.go
index f0ad33b..5582c8a 100644
--- a/cc/testing.go
+++ b/cc/testing.go
@@ -263,6 +263,7 @@
 		"Android.bp":  []byte(bp),
 		"foo.c":       nil,
 		"bar.c":       nil,
+		"baz.o":       nil,
 		"a.proto":     nil,
 		"b.aidl":      nil,
 		"sub/c.aidl":  nil,