add variant_version property to apexBundle

This property allows modifying the variant version that is put into the
APEX manifest.

Bug: 285138555
Change-Id: I42b8c0ddad8822a0a329e99ec4ec62f8c3546ee9
diff --git a/apex/apex.go b/apex/apex.go
index 69eea03..492e4f0 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -224,6 +224,9 @@
 	// Name that dependencies can specify in their apex_available properties to refer to this module.
 	// If not specified, this defaults to Soong module name.
 	Apex_available_name *string
+
+	// Variant version of the mainline module. Must be an integer between 0-9
+	Variant_version *string
 }
 
 type ApexNativeDependencies struct {