Explicitly specify --api-class-resolution api for metalava

Previously, `--api-class-resolution api` was the default if that option
was not specified but the other change in this topic is switching it to
`--api-class-resolution api:classpath` to match the behavior in
AndroidX. This change explicitly specifies the option needed by Soong's
use of metalava.

Bug: 285140653
Test: m checkapi
Change-Id: Ief3c7f9dfdfa946f21cb048a579ec90309fb350f

java/java.go

@@ -1728,6 +1728,10 @@ func metalavaStubCmd(ctx android.ModuleContext, rule *android.RuleBuilder,
 		FlagWithArg("--hide ", "InvalidNullabilityOverride").
 		FlagWithArg("--hide ", "ChangedDefault")
 
+	// Force metalava to ignore classes on the classpath when an API file contains missing classes.
+	// See b/285140653 for more information.
+	cmd.FlagWithArg("--api-class-resolution ", "api")
+
 	return cmd
 }