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>