RFR: JDK-8207001: *.obj.log files get truncated causing unreliable incremental builds on Windows

[Tim Bell]

Erik, Ralf:

> Please review this fix for problem 1 described below. The patch is
> basically what Ralf suggested.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8207001
> Webrev: http://cr.openjdk.java.net/~erikj/8207001/webrev.01/

Looks good.

/Tim