I messed up the spelling of '-stack_size' making it '-stack' instead.
Will need to fix on master branch. But let's test this here before
making another master branch commit.
In particular, these two changes are relevant:
* zig cc: support -stack in addition to --stack for linker arg
- Fixes stack overflow when running zig2 on aarch64-macos.
* compiler_rt: avoid using weak aliases
- Fixes duplicate symbol when linking zig2 on aarch64-linux.
Override the cache directories because they won't actually help other CI
runs which will be testing alternate versions of zig, and ultimately
would just fill up space on the hard drive for no reason.
In practice we did see one of the CI servers fill up too many files
inside ~/.cache/zig, which caused certain file system operations to
start returning ENOSPC, despite the hard drive having plenty of space
left.
