Add test for missing Java build system

Author: smowton

java/ql/integration-tests/all-platforms/java/diagnostics/no-build-system/Test.java

@@ -0,0 +1 @@
+class Test {}

java/ql/integration-tests/all-platforms/java/diagnostics/no-build-system/diagnostics.expected/java-autobuilder.json

@@ -0,0 +1 @@
+{"timestamp":1674235729,"source":{"id":"java/autobuilder/no-build-command","name":"No build command found","extractorName":"java"},"markdownMessage":"Could not find a Gradle, Maven or Ant top-level project to build. Please [TODO](supply a manual build command)","severity":"error","visibility":{"statusPage":true,"cliSummaryTable":true,"telemetry":true}}

java/ql/integration-tests/all-platforms/java/diagnostics/no-build-system/test.py

@@ -0,0 +1,8 @@
+import os
+from create_database_utils import *
+from diagnostics_test_utils import *
+
+os.mkdir("diagnostics")
+run_codeql_database_create([], lang="java", runFunction = runUnsuccessfully, db = None, extra_env = {"CODEQL_EXTRACTOR_DIAGNOSTIC_DIR": "diagnostics"})
+
+check_diagnostics(test_dir = ".", diagnostics_dir = "diagnostics")