fix iOS OpenJDK and simulator builds

With the iOS openjdk-src build, sun.misc.Launcher will throw an
InternalError if avian.file.Handler is not present, so let's make it
happy.

Also, as of recent version(s) of Xcode, there are no utilities
(e.g. ar and strip) in iPhoneSimulator.platform/usr/bin, so we can
just use the system ones.
Merge pull request #262 from dicej/ios

fix iOS OpenJDK and simulator builds