Avoid hardcoded `-XX:+UseZGC` on BSD system?

[catap]

Unfortently, OpenJDK does'n support ZGC on BSD system, an attempt to enable it on cofigure fails as:

checking if platform is supported by ZGC... no, bsd-x86_64
checking if JVM feature 'zgc' is available... no

See: https://github.com/openjdk/jdk/blob/027607968b3d55b498e9f2d7a4023b8ae2d47b5b/make/autoconf/jvm-features.m4#L318-L327

This mean that attempt to use bloop on any bsd system fails as:

~ $ scala --power bloop output
Error occurred during initialization of VM
Option -XX:+UseZGC not supported
~ $ 

as temporarry workaround a user may do something like this:

env BLOOP_JAVA_OPTS="-XX:+UseParallelGC"  scala --power bloop output

but, I think, that default hardcoded option should be adjusted.

And yes, ShenandoahGC is available on BSD system if you think that low latency GC is requried here.

[tgodzik]

Thanks for reporting! It should be easy to check the current platform and change the defaults at https://github.com/scalacenter/bloop/blob/7bac89a5a7c5098909a6fc489fe099766a2dd00d/bloop-rifle/src/main/scala/bloop/rifle/BloopRifleConfig.scala#L75

I might not have time to fix it soon though.