This change refactors the `zig` argument handling (for `build-lib`, etc.
commands) to use a `process.argsWithAllocator` iterator instead of
directly accessing arguments via array indices. This supports the next
commit which will enable us to use a response file argument iterator
here seamlessly.

Helps #10693

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

This change enables `zig build-lib` and friends to take a response file
of command line arguments, for example:

```sh
zig build-lib @args.rsp
```

Which effectively does the same thing as this in Bash:

```sh
zig build-lib $(cat args.rsp)
```

Being able to use a file for arguments is important as one can quickly
exceed the 32 KiB limit that Windows imposes on arguments to a process.

Helps #10693

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

In Mach engine we're seeing command line arguments to `zig build-lib`
exceed the 32 KiB limit that Windows imposes, due to the number of
sources and compiler flags we must pass in order to build gpu-dawn.

This change fixes the issue by having `Builder` check if the arguments
to a `zig build-*` command are >30 KiB and, if so, writes the arguments
to a file `zig-cache/args/<SHA2 of args>`. Then the command invocation
merely becomes `zig build-lib @<that file>`.

Fixes #10693

Fixes hexops/mach#167

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>