RFR: 8155824: JDK build should tune down small apps more aggressively

[Claes Redestad]

Hi build-dev!

I recently discovered that running with -XX:TieredStopAtLevel=1 can 
speed up jmod execution a bit:

http://mail.openjdk.java.net/pipermail/jigsaw-dev/2016-May/007593.html

Applying this to the runner itself might be a mouthful, but it seems 
profitable to apply this to JDK
build itself. The question was raised if we would get benefits elsewhere 
if we apply it to all "small"
java targets...

Some experimental results on my machine:

time make images

real    2m39.281s
user    42m15.164s
sys    3m56.388s

-XX:TieredStopAtLevel=1 for jmod target only:

real    2m34.913s
user    38m18.112s
sys    3m44.528s

-XX:TieredStopAtLevel=1 for all small java targets in makefiles:

real    2m29.490s
user    35m45.944s
sys    3m33.428s

Reports indicate the real time improvement is even better on smaller 
machines.

I thus propose this patch:
http://cr.openjdk.java.net/~redestad/8155824/webrev.01/

Bug: https://bugs.openjdk.java.net/browse/JDK-8155824

Thanks!

/Claes