RFR(XS): 8164939: GTest LogDecorations.iso8601_time_test fails on macOS

[Marcus Larsson]

Hi,

Please review the following patch fixing a daylight savings issue with 
mktime/localtime in the unit tests on Mac OSX. Avoiding the use of 
'daylight' and instead letting mktime handle DST seems to solve the 
issue, and still works as intended on all the other platforms.

Webrev:
http://cr.openjdk.java.net/~mlarsson/8164939/webrev.00/

Issue:
https://bugs.openjdk.java.net/browse/JDK-8164939

Testing:
Manually verified on a previously failing host. Unit tests through JPRT.

Thanks,
Marcus