Ensure jdks when running compiledump

If we want this to be easier for external people to run different version on a dump they can now simply do:
$ git clone https://r8.googlesource.com/r8
$ cd r8
$ tools/compiledump.py -d mydump --version A.B.C-dev

Change-Id: I2cbb20bd413f48bc217343bf87bd75ffdb9b7eaa
diff --git a/tools/compiledump.py b/tools/compiledump.py
index 66a2152..c819865 100755
--- a/tools/compiledump.py
+++ b/tools/compiledump.py
@@ -789,6 +789,7 @@
 
 
 def run(args, otherargs):
+    gradle.EnsureJdk()
     if args.summary:
         summarize_dump_files(otherargs)
     elif args.loop: