Use result.Config.PrebuiltOS() to get prebuiltHost in test_spec_test

Bug: 312536783
Bug: 312536905
Test: m nothing --no-skip-soong-tests -j96

Ignore-AOSP-First: CPing test_spec rule to udc-mainline-prod to support migration of test targets. Cherry pick of:aosp/2836072

Change-Id: I1e12281927269d42ae796348b223030acfd6ecfa
Merged-In: I1e12281927269d42ae796348b223030acfd6ecfa
diff --git a/java/test_spec_test.go b/java/test_spec_test.go
index 22a8e60..39aff4c 100644
--- a/java/test_spec_test.go
+++ b/java/test_spec_test.go
@@ -86,7 +86,8 @@
 	// Tests for all_test_spec singleton.
 	singleton := result.SingletonForTests("all_test_specs")
 	rule := singleton.Rule("all_test_specs_rule")
-	expectedCmd := "out/soong/host/linux-x86/bin/metadata -rule test_spec -inputFile out/soong/all_test_spec_paths.rsp -outputFile out/soong/ownership/all_test_specs.pb"
+	prebuiltOs := result.Config.PrebuiltOS()
+	expectedCmd := "out/soong/host/" + prebuiltOs + "/bin/metadata -rule test_spec -inputFile out/soong/all_test_spec_paths.rsp -outputFile out/soong/ownership/all_test_specs.pb"
 	expectedOutputFile := "out/soong/ownership/all_test_specs.pb"
 	expectedInputFile := "out/soong/.intermediates/module-name/intermediateTestSpecMetadata.pb"
 	if !strings.Contains(