Boot cycle builds

[Brad Wetmore]

> As soon as we can do a jdk7 boot cycle build again, I plan on changing
> the default build to include a boot cycle build
> (where the jdk7 image is built, then used as the boot jdk to build
> it again).

Kelly, is this just when doing full "control"/top-level builds?  Not
when building just the JDK repository?

> It can be turned off with SKIP_BOOT_CYCLE=true, but I hope the
> integrators and everyone will be careful when it is turned off.

Looks like this is already in?  (./Makefile)

> Depending on your build situation, this could add 20-30 minutes
> (maybe more) to your jdk7 build, which is painful I know, but
> so is finding out that the jdk you just built doesn't work.

If not, I'll need to adjust my security builds accordingly.

Brad