Support Windows

Author: dnestoro

common/junit-platform-native/src/main/java/org/graalvm/junit/platform/NativeImageJUnitLauncher.java

@@ -55,6 +55,7 @@
 import org.junit.platform.launcher.listeners.UniqueIdTrackingListener;
 import org.junit.platform.reporting.legacy.xml.LegacyXmlReportGeneratingListener;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.UncheckedIOException;
@@ -218,15 +219,15 @@ private static Path getTestIDsFromDefaultLocations() {
     }
 
     private static Path getGradleTestIdsDefaultLocation() {
-        return Path.of(getBuildDirectory("/build/"))
+        return Path.of(getBuildDirectory(File.separator + "build" + File.separator))
                 .resolve("test-results")
                 .resolve("test")
                 .resolve("testlist")
                 .toAbsolutePath();
     }
 
     private static Path getMavenTestIDsDefaultLocation() {
-        return Path.of(getBuildDirectory("/target/"))
+        return Path.of(getBuildDirectory(File.separator + "target" + File.separator))
                 .resolve("test-ids")
                 .toAbsolutePath();
     }