Kotlin: Add a test for path transformers

java/ql/integration-tests/all-platforms/kotlin/path_transformer/classes.expected

@@ -0,0 +1 @@
+| file:///src/kotlin_source.kt:1:1:2:1 | Foo |

java/ql/integration-tests/all-platforms/kotlin/path_transformer/classes.ql

@@ -0,0 +1,5 @@
+import java
+
+from Class c
+where c.fromSource()
+select c

java/ql/integration-tests/all-platforms/kotlin/path_transformer/kotlin_source.kt

@@ -0,0 +1,2 @@
+class Foo {
+}

java/ql/integration-tests/all-platforms/kotlin/path_transformer/test.py

@@ -0,0 +1,14 @@
+from create_database_utils import *
+
+path_transformer_file = 'path_transformer'
+root = os.getcwd().replace('\\', '/')
+with open(path_transformer_file, 'w') as f:
+    f.write('#/src\n' + root + '//\n')
+os.environ['SEMMLE_PATH_TRANSFORMER'] = root + '/' + path_transformer_file
+
+run_codeql_database_create(["kotlinc kotlin_source.kt"], lang="java")
+files = ['test-db/trap/java/src/kotlin_source.kt.trap.gz', 'test-db/src/src/kotlin_source.kt']
+exists = list(map(os.path.exists, files))
+if exists != [True] * 2:
+    print(exists)
+    raise Exception("Didn't get expected filed")