Pass jvm_flags through scala_benchmark_jmh

[jeremyrsmith]

Description

Passes jvm_flags through scala_benchmark_jmh.

Motivation

JVM flags can sometimes be necessary to run a java program (for example, when it depends on a library that needs --add-opens). Without passing it through to scala_binary, there's no way to accomplish this for a benchmark.

[jeremyrsmith]

@mbland @simuons @WojciechMazur any chance of getting this reviewed/merged? It's pretty small. Thanks!

[mbland]

@jeremyrsmith Sorry, I was on vacation all last week and forgot to mention that beforehand. I'm also in crunch mode preparing for a quick trip/leading a training for the next two days.

Before approving/merging, please add a test:

• Add a small benchmark to //test/jmh that won't work without this.
• Add a test case to the JMH block of test_misc.sh to demonstrate that it works as intended.
• Add a line at the end of test_misc.sh to run the test case. (There's a new helper I've been using to avoid having to add such lines explicitly, but don't worry about that for now.)

[jeremyrsmith]

Thanks, will do!