Enable compiler on NetBSD, DragonFly, illumos and Solaris

[ncruces]

This culminates this series of changes, enabling the compiler on:

• NetBSD amd64 and arm64
• DragonFly BSD amd64
• illumos amd64
• Solaris amd64

We're not currently testing arm64 for either FreeBSD or NetBSD, but I've tested them. The emulation is slow, I'm not sure if it's worth it. The others are not supported Go arm64 targets.

OpenBSD was not added because it failed with an SIGSEGV. If anyone wants to take a stab at this, I'd welcome it.

[ncruces]

Just adding a note that #2345 essentially disables the compiler on arm64 NetBSD.

It can be force enabled with wazero.NewRuntimeConfigCompiler() (which disables CPU detection), but you run the risk of crashes at runtime (if your CPU doesn't support the necessary instructions).

[anuraaga]

@ncruces Just to understand why does #2345 (excellent pr number by the way) disable it? I figured it would use compiler as long as it's arm 8.1 even on NetBSD. Or does the OS actually expose feature flags differently?

Edit: oops got it, didn't realize they would be hidden from apps on certain OSes, that's interesting.

[ncruces]

This should offer a good explanation:
https://kernel.org/doc/Documentation/arm64/cpu-feature-registers.txt

Unlike the Intel CPUID instruction, these ARM registers are not made available to user space.

Linux and FreeBSD do make them available, somehow (which I don't fully understand), but on other OSes just running that code crashes the process.

Any other OS where this works, I'm OK with whitelisting, but these are the only two in the Go codebase. So I only run feature detection for those two OSes.

On macOS we can assume the chip supports it (on desktop macOS the M1 is ARMv8.4, and iOS doesn't even support a JIT).

On Windows, Windows 11 requires these, Windows 10 doesn't. Given the big recent push, I argue that Windows 11 covers most of the target systems.

[ncruces]

This also means that post #2345 is not a regression vs v1.8.1: the only systems where we disable the compiler by default, are the ones were sure are missing instructions (amd64 without SSE4.1 or arm64 without atomics), and you can still force enable the compiler anyway.