RFR: JDK-8170280: Enable -g for all java compilation in the build

[Erik Joelsson]

For a long time, a lot of people have been wanting the JDK classes to be 
compiled with debug symbols enabled by default. I believe the reason we 
haven't so far is to keep footprint down for the JRE image. The usecase 
for debug information is mainly in the JDK image, which is used for 
development. The problem so far has then been that we don't want to 
compile everything twice, once with and once without debug symbols.

With jlink, we now have the option of stripping debug information at 
link time. This adds a bit of time creating the images, but it's small 
compared to recompiling all classes. Because of this, I propose that we 
enable debug symbols for all java compilation in the build by default 
and add stripping to all images that are footprint sensitive.

Bug: https://bugs.openjdk.java.net/browse/JDK-8170280

Webrev: http://cr.openjdk.java.net/~erikj/8170280/webrev.top.01

/Erik