Handle the case where the release value set is a list.

Bug: 304814040
Test: CI, unit test,
b build build/make/tools/aconfig:aconfig.test.cpp
b test build/make/tools/aconfig:AconfigJavaHostTest

Change-Id: I9ca939348a063c39e9528f24e788f9757458d30c
diff --git a/android/variable.go b/android/variable.go
index 006a77f..ab6dfef 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -474,8 +474,8 @@
 	ProductBrand        string   `json:",omitempty"`
 	BuildVersionTags    []string `json:",omitempty"`
 
-	ReleaseVersion          string `json:",omitempty"`
-	ReleaseAconfigValueSets string `json:",omitempty"`
+	ReleaseVersion          string   `json:",omitempty"`
+	ReleaseAconfigValueSets []string `json:",omitempty"`
 
 	ReleaseAconfigFlagDefaultPermission string `json:",omitempty"`