[metif12]

main does not build timeout. This is the one-line cause and its fix.

The break

The tip commit c6cbc320b6 ("timeout: fix errors") changed every
terminate_process to take the process by value, but left the two calls
that mutate it:

src/timeout/timeout_windows.c.v:13:3: error: `p` is immutable, declare it with `mut` to make it mutable
src/timeout/timeout_windows.c.v:15:3: error: `p` is immutable, declare it with `mut` to make it mutable

fn terminate_process(p os.Process, sig_num int, process_group bool) {
	if sig_num == 15 {
		p.signal_term()
	} else {
		p.signal_kill()
	}
}

Reproduced on c6cbc320b6: v -o timeout.exe src/timeout fails with exactly
those two errors. The Windows build of timeout is broken on main.

Why it went unnoticed

CI has been failing inside the V compiler's own bootstrap before it compiles
any of this repository, on every job, since early October. Every PR in the
repo shows red, which is what upstream issues
vlang/v#30551,
#30598 and
#30753 track. So there has been no
green signal to catch this.

The fix

The comment already sitting above that function says why a value cannot
work:

A pointer, because signalling a process changes it. Passing it by value, as
the nix version can, made the compiler reference it for us and then reject
that as deprecated automatic referencing.

So the signature is what has to move back, not the comment. All three
platform variants take mut p &os.Process, and both call sites pass mut &p
— which is what the tree had before c6cbc320b6, and the only combination of
those two choices that compiles.

The three variants have to agree, because timeout.v calls whichever one the
target selects from a single shared call site. A mismatch is a build break on
exactly whichever platform picks the odd one out, which is the failure mode
the vinix-cross-build job in #250 is meant to catch.

Verification

• v -o timeout.exe src/timeout builds on c6cbc320b6 + this commit, and
  does not build on c6cbc320b6 alone.
• src/timeout passes 1/1 with a real GNU timeout on PATH to compare
  against.
• v fmt -verify clean on all four files.
• The diff is five lines: three signatures and two call sites, nothing else.

Note for review

This is deliberately minimal and lands ahead of #250, which was written
against the pre-c6cbc320b6 tree and carries the same signature fix. Once
this merges, #250's src/timeout commit rebases away and that PR is left
carrying only the Vinix build target.