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/rust/project_json_test.go b/rust/project_json_test.go
index 09d30db..bdd54c5 100644
--- a/rust/project_json_test.go
+++ b/rust/project_json_test.go
@@ -176,6 +176,8 @@
 }
 
 func TestProjectJsonBindGen(t *testing.T) {
+	buildOS := android.TestConfig(t.TempDir(), nil, "", nil).BuildOS
+
 	bp := `
 	rust_library {
 		name: "libd",
@@ -214,9 +216,9 @@
 		if strings.Contains(rootModule, "libbindings1") && !strings.Contains(rootModule, "android_arm64") {
 			t.Errorf("The source path for libbindings1 does not contain android_arm64, got %v", rootModule)
 		}
-		if strings.Contains(rootModule, "libbindings2") && !strings.Contains(rootModule, android.BuildOs.String()) {
+		if strings.Contains(rootModule, "libbindings2") && !strings.Contains(rootModule, buildOS.String()) {
 			t.Errorf("The source path for libbindings2 does not contain the BuildOs, got %v; want %v",
-				rootModule, android.BuildOs.String())
+				rootModule, buildOS.String())
 		}
 		// Check that libbindings1 does not depend on itself.
 		if strings.Contains(rootModule, "libbindings1") {