[minor] Add project.basedir system property, use in CliFrontendTestUtils

Before, we were relying on the current working directory, which is
unreliable and can change, depending on where/how tests are executed.

flink-clients/src/test/java/org/apache/flink/client/cli/CliFrontendTestUtils.java

@@ -25,6 +25,8 @@
 import java.io.FileNotFoundException;
 import java.io.PrintStream;
 import java.net.MalformedURLException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 
 import static org.junit.Assert.assertEquals;
 
@@ -44,7 +46,9 @@ public class CliFrontendTestUtils {
  private static final PrintStream previousSysout = System.out;
 
  public static String getTestJarPath() throws FileNotFoundException, MalformedURLException {
- File f = new File("target/maven-test-jar.jar");
+ String projectBaseDir = System.getProperty("project.basedir");
+ Path testJarPath = Paths.get(projectBaseDir, "target", "maven-test-jar.jar");
+ File f = testJarPath.toFile();
  if (!f.exists()) {
  throw new FileNotFoundException("Test jar not present. Invoke tests using maven "
  + "or build the jar using 'mvn process-test-classes' in flink-clients");

pom.xml

@@ -1548,6 +1548,7 @@ under the License.
  <log4j.configuration>${log4j.configuration}</log4j.configuration>
  <hadoop.version>${hadoop.version}</hadoop.version>
  <execution.checkpointing.unaligned>true</execution.checkpointing.unaligned>
+ <project.basedir>${project.basedir}</project.basedir>
  </systemPropertyVariables>
  <argLine>-Xms256m -Xmx2048m -Dmvn.forkNumber=${surefire.forkNumber} -XX:+UseG1GC</argLine>
  </configuration>