Add/fix tests for new shadow stack allocation scheme.

[vext01]

Requires ykjit/ykllvm#220 (and a ykllvm sync)

[ltratt]

Please force push a ykllvm sync.

[vext01]

I rebased, synced ykllvm and force pushed.

(The "compare" contains what I assume is the result of the rebase, so may contain more than you expected)

[vext01]

hold off this for a moment, just realised the rebase causes test failures.

[vext01]

test fixed with another force push.

[ltratt]

Probably this means that we can delete peel1.swt.c and remove || test "$YKB_TRACER" = "swt" from peel1.c. In other words, we can probably use one test for both hwt and swt, which would be nice!

[vext01]

test seems to pass, so great.

[vext01]

(force pushed, btw)

[ltratt]

Thanks!