jdk8 Build changes

[Kelly O'Hair]

Excuse the wide mailing, but it was important to try and reach anyone building jdk8.

The jdk8/build repositories at http://hg.openjdk.java.net/jdk8/build have been changed to use the new
build-infra "configure&make" build setup, so it is official, but it still needs to be integrated into the
main jdk8/jdk8 repositories at http://hg.openjdk.java.net/jdk8/jdk8. This is expected to happen
in 2 weeks.

A few bullet points:

* ANY changes to ANY make/ files from now until we integrate into jdk8/jdk8 represents a risk, please talk to us first.
* Windows CYGWIN 1.7.16+ will be required, MKS will no longer work.
* This only applies to builds being done from the top repository, i.e. building the entire JDK
* Should be faster in all cases, however we have seen some cases where the benefit is slight, depends on the machine&disk used.
* The highly parallel building could swamp some systems, you may need to use "make JOBS=2" to dial it down
* For a limited time, the old Makefiles can still be used with "make NEWBUILD=false"
* Also for a limited time, people allergic to using "configure" can try "make bridgeBuild"

Please let us know about any issues you encounter, if you have access to JBS to file the issue please do so,
use component=infrastructure and subcomponent=build, and add the label "build-infra".
If you don't have access to JBS, provide us the details and we will file the issue for you.

-kto