RFR [XS]: 8248429: Add --enable-preview as VM argument when running microbenchmarks

[Claes Redestad]

On 2020-06-30 18:40, Magnus Ihse Bursie wrote:
>>
>> An alternative workaround would be to add
>> @Fork(jvmArgsAppend = "--enable-preview") to all micros, whether
>> they use preview features or not. Perhaps that wouldn't be so bad,
>> actually.
> That sounds like a reasonable compromise, yes.

Well, it moves the responsibility to micro authors, while violating the
principle of least surprise in some ways.

I think my preference would be some means to ask javac to not tag
.class files with the 65535 minor version unless there's some actual
preview feature usage (which I think is what the --enable-preview flag
should do by default, but I guess someone has insisted on the current 
behavior to get more of a fail fast behavior).

Second to that a solution in the build would be preferable - if we can
come up with something that has infinitesimal impact to build times.

Adding --enable-preview to every micro would be a reasonable workaround,
for now, but I view it as a temporary hack.

/Claes