Speed up a "big stack" test, and test Winch

[alexcrichton]

This test currently takes 50s locally in debug mode locally so optimize it by disabling optimizations in Cranelift and additionally using the single-pass register allocator. This drops the test time to ~3s locally.

[alexcrichton]

A good question! I did a bit more digging and I've now changed this to:

• This is tested on both Winch and Cranelift now.
• Cranelift disables egraph optimizations
• Cranelift uses the single-pass register allocation pass

That makes the test much speedier now so it will continue to test Cranelift.

[pchickey]

Thanks. Comment needs a fix, then its good to go

[alexcrichton]

oops, thanks!