Remove -Xcheckinit compiler flag

[armanbilge]

I'm pretty sure this is responsible for those auto-generated volatile fields that have been taunting @vasilmkd 😆

[vasilmkd]

I'm in favor of removing this, because it causes a volatile field bitmap$init to be created on a lot of classes. This slows down constructors and field accesses (which we work hard to avoid), but the constructors remain. Examples:
#2534 (comment) and #2473.

[armanbilge]

I don't know how hard it would be to setup, but if this check is important, maybe we can enable this flag only for testing/CI but remove for release?

[vasilmkd]

No, I don't agree with that. That could hide bugs. Either there is a good reason that this flag was included and @djspiewak can shed some light on it, or I really don't know why this is here and we can remove it everywhere.

[armanbilge]

Btw it was introduced here:
de1f68b#diff-928a6eabff1094f1b64a2d1b6bc7574c5a483476ec3fee98c16d1fe46aae9d0d

[vasilmkd]

Before:

[info] Benchmark             (size)   Mode  Cnt      Score     Error  Units
[info] AsyncBenchmark.start     100  thrpt    5  12890.043 ± 107.889  ops/s

After:

[info] Benchmark             (size)   Mode  Cnt      Score     Error  Units
[info] AsyncBenchmark.start     100  thrpt    5  15683.946 ± 296.763  ops/s

[djspiewak]

Sincerely no idea why I explicitly added this. So odd.

[armanbilge]

@vasilmkd should we consider reverting some of the changes you made to workaround this? E.g. moving things into constructors. Or maybe those were good ideas anyway 👍