Rewrite create-jctf-tests.sh in python

Bug:
Change-Id: I6d79c852b5118d2e5b9ae8f46823961ac364e7ed
diff --git a/build.gradle b/build.gradle
index 695e898..6667647 100644
--- a/build.gradle
+++ b/build.gradle
@@ -326,12 +326,11 @@
 
 task createJctfTests(type: Exec) {
     def outputDir = "build/generated/test/java/com/android/tools/r8/jctf"
-    def script = "scripts/create-jctf-tests.sh"
+    def script = "tools/create_jctf_tests.py"
     inputs.file script
     outputs.dir outputDir
     dependsOn downloadDeps
-    executable "bash"
-    args "${projectDir}/${script}"
+    commandLine "python", script
     workingDir = projectDir
 }