RFR 8233844: Add LogCompilation build artifacts to .gitignore

[Jorn Vernee]

Hi,

I'd like to contribute this very small patch that adds some 
LogCompilation build artifacts to the .gitignore file.

Bug: https://bugs.openjdk.java.net/browse/JDK-8233844
Webrev: http://cr.openjdk.java.net/~jvernee/8233844/webrev.00/index.html

Testing = manual

FWIW, it seems that these artifacts are produced at some point either 
while doing a vanilla build, or when running the test, so these 
artifacts will show up pretty much always when using Git (AFAICS I have 
them in all my OpenJDK Git repos, and I've never directly used this 
utility). So, it seems worth it to gitnore them.

As a heads-up; I'm not a committer on the JDK project, so a sponsor 
would need to push this.

Thanks,
Jorn