Work around break block issues in Kawa

Fixes #1230

Change-Id: I1eb4579f4873d2e60b357acd463dbbd77261c936

appinventor/buildserver/src/com/google/appinventor/buildserver/resources/runtime.scm

@@ -806,8 +806,18 @@
       (let *yail-loop* ()
         (if ,condition
             (begin
-              (begin ,body . ,rest)
-              (*yail-loop*))
+              ;; Kawa attempts to be smart by detecting unreachable
+              ;; code and reporting it as an error. This causes an
+              ;; issue here if *yail-break* is determined to be always
+              ;; called within body-form, since *yail-loop* will
+              ;; unreachable. The mixing of `or` and `and` operators
+              ;; below fools the Kawa optimizer so that even in
+              ;; trivial cases it won't flag the call to *yail-loop*
+              ;; as unreachable. It also works around a bug in the
+              ;; tail-recursive optimizer that breaks when the while
+              ;; loop is empty.
+              (or (and ((lambda () (begin ,body . ,rest))) #f)
+                  (*yail-loop*)))
             #!null)))))
 
 ;; Below are hygienic versions of the forrange, foreach and while