RFR: JDK-8216021: RunTest.gmk might set concurrency level to 1 on Windows

[Tim Bell]

Erik:

> When running tests using "make run-test-prebuilt" on Windows, the
> calculation of available memory may fail. This only happens on certain
> systems, and is likely related to which version of Cygwin that is being
> used. The consequence is that concurrency gets set to 1. The cause of
> the problem is mishandling of Windows \r line endings, which Cygwin
> tools are known to handle differently in different versions.
>
> To fix the problem here, I've added explicit filtering of \r before
> trying to interpret the memory size as a number.
>
> I checked the corresponding construct in configure, and it seems to work
> on the same machine where RunTestsPrebuilt.gmk failed, so I left it alone.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8216021
>
> Webrev: http://cr.openjdk.java.net/~erikj/8216021/webrev.01/

Looks good.

Tim