RFR(xs): 8172712: configure should check that grep handles empty pattern correctly

[Mikael Vidstedt]

I also ran into this problem a couple of weeks ago with some other "misbehaving” grep. Thanks for adding this check!

Cheers,
Mikael

> On Jan 12, 2017, at 5:04 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> 
> Dear all,
> 
> please take a look at this fix. This should prevent configure from using a grep which is not able to handle pattern lists with empty patterns.
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8172712 <https://bugs.openjdk.java.net/browse/JDK-8172712>
> 
> webrevs:
> http://cr.openjdk.java.net/~stuefe/webrevs/8172712-configure-should-check-that-grep-handles-empty-pattern-correctly/webrev.00/webrev/ <http://cr.openjdk.java.net/~stuefe/webrevs/8172712-configure-should-check-that-grep-handles-empty-pattern-correctly/webrev.00/webrev/>
> 
> Background:
> 
> https://bugs.openjdk.java.net/browse/JDK-8172579 <https://bugs.openjdk.java.net/browse/JDK-8172579> was a build error caused by a buggy grep (on AIX) and the easiest way to work around that bug would be to use the GNU version of grep. It was suggested in the orginal mail thread (http://mail.openjdk.java.net/pipermail/build-dev/2017-January/018495.html <http://mail.openjdk.java.net/pipermail/build-dev/2017-January/018495.html>) to check this in configure.
> 
> This change implements this suggestion and checks if grep behaves correctly.
> 
> Kind Regards, Thomas