WASI support

[QuantumSegfault]

Rationale

Adds support for WASI (p1 & p2; wasi-libc) to Phobos. This builds on prior work done in DRuntime to support the same targets (largely using wasi-libc's POSIX emulation).

Pre-review checklist

• I have performed a self-review of my code.
  • This code has also already been reviewed and merged in LDC by @kinke. This is a cherry-pick of the changes. I checked that there are no faulty conflict resolutions, but did NOT verify that support is 100% complete with anything new master Phobos may have added.
• If my PR fixes a bug or introduces a new feature, I have added thorough tests.
  • No new tests are added to Phobos, but the existing unittests are run during LDC CI for both WASIp1 and WASIp2 targets.
• If my changes are non-trivial and do not concern a reported issue, I have added a changelog entry.
  • I did NOT add an entry, as these changes do not impact upstream DMD's Phobos, and are only visible in LDC.

[QuantumSegfault]

@kinke
@thewilsonator

[thewilsonator]

Enforce Allman style
grep -nrE '(if|for|foreach|foreach_reverse|while|unittest|switch|else|version) .*{$' $(find etc std -name '*.d'); test $? -eq 1
std/socket.d:1153:        else {
std/socket.d:1733:    else {
std/socket.d:2612:version (CRuntime_WASI) {
std/datetime/systime.d:2706:            else {
std/parallelism.d:4436:    version (WASI) {

braces on newlines

[thewilsonator]

ping when this is green

[0xEAB]

Style check fails due to:

• std/file.d(2284:6)[warn]: Public declaration 'setAttributes' has no documented example.
• std/file.d(3533:17)[warn]: Public declaration 'thisExePath' has no documented example.
• std/file.d(3683:16)[warn]: Local imports should specify the symbols being imported to avoid hiding local symbols.
• std/file.d(5614:7)[warn]: Public declaration 'getAvailableDiskSpace' has no documented example.
• std/typecons.d(3533:10)[warn]: Public declaration 'UnqualRef' has no documented example.

[QuantumSegfault]

Style check fails due to:

* `std/file.d(2284:6)[warn]`: Public declaration 'setAttributes' has no documented example.

* `std/file.d(3533:17)[warn]`: Public declaration 'thisExePath' has no documented example.

* `std/file.d(3683:16)[warn]`: Local imports should specify the symbols being imported to avoid hiding local symbols.

* `std/file.d(5614:7)[warn]`: Public declaration 'getAvailableDiskSpace' has no documented example.

* `std/typecons.d(3533:10)[warn]`: Public declaration 'UnqualRef' has no documented example.

I saw (but thanks for the nice extract). Just didn't get to it yet. Just starting now.

[QuantumSegfault]

@thewilsonator

The three external CI runs all pass.

But all the GHA checks are stalling.

[0xEAB]

I saw (but thanks for the nice extract). Just didn't get to it yet. Just starting now.

No rush. Didn’t mean to stress you, sorry.
(Just wanted to point out what’s left to do.)

[0xEAB]

But all the GHA checks are stalling.

Caused by the ongoing GitHub outage:

Workflow runs are still failing, and jobs may remain queued for an extended period before starting or may time out. Jobs using GitHub-hosted runners are particularly affected while capacity is constrained.

— https://www.githubstatus.com/

[QuantumSegfault]

1 workflow awaiting approval