Add top-level Makefile target for running gtest

[Erik Joelsson]

Looks good!

/Erik

On 2016-05-17 10:16, Erik Helin wrote:
> Hi all,
>
> this small patch adds a top-level Makefile target for conveniently
> running the gtest unit tests.
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8157028
>
> Webrev:
> http://cr.openjdk.java.net/~ehelin/8157028/webrev.00/
>
> Testing:
> - Running locally on Linux x86-64
>
> Thanks,
> Erik