Replace android.BuildOs with Config.BuildOS

Replace the android.BuildOs constant with Config.BuildOS so that it
can vary based on the product config.

Bug: 190084016
Test: all Soong tests
Change-Id: Ia67f872d8b2ab788747a22e3a9659dc21c9775cd
diff --git a/java/kotlin_test.go b/java/kotlin_test.go
index fd2f3ca..db30696 100644
--- a/java/kotlin_test.go
+++ b/java/kotlin_test.go
@@ -15,10 +15,11 @@
 package java
 
 import (
-	"android/soong/android"
 	"strconv"
 	"strings"
 	"testing"
+
+	"android/soong/android"
 )
 
 func TestKotlin(t *testing.T) {
@@ -114,7 +115,7 @@
 	t.Run("", func(t *testing.T) {
 		ctx, _ := testJava(t, bp)
 
-		buildOS := android.BuildOs.String()
+		buildOS := ctx.Config().BuildOS.String()
 
 		kapt := ctx.ModuleForTests("foo", "android_common").Rule("kapt")
 		kotlinc := ctx.ModuleForTests("foo", "android_common").Rule("kotlinc")
@@ -182,7 +183,7 @@
 			android.FixtureMergeEnv(env),
 		).RunTestWithBp(t, bp)
 
-		buildOS := android.BuildOs.String()
+		buildOS := result.Config.BuildOS.String()
 
 		kapt := result.ModuleForTests("foo", "android_common").Rule("kapt")
 		javac := result.ModuleForTests("foo", "android_common").Description("javac")