Wasm backend testsuite failure: internal error: ffi_alloc_prep_closure failed: 4

T4221, T4038 fails with something like:

T4221: internal error: ffi_alloc_prep_closure failed: 4
    (GHC version 9.5.20221211 for wasm32_unknown_wasi)
    Please report this as a GHC bug:  https://www.haskell.org/ghc/reportabug
error: Uncaught (in promise) RuntimeError: unreachable
    at abort (wasm://wasm/01b05c4e:1:5923853)
    at rtsFatalInternalErrorFn (wasm://wasm/01b05c4e:1:1511015)
    at barf (wasm://wasm/01b05c4e:1:1511391)
    at createAdjustor (wasm://wasm/01b05c4e:1:1684864)
    at _blk_c1ID (wasm://wasm/01b05c4e:1:155586)
    at StgRun (wasm://wasm/01b05c4e:1:1568771)
    at scheduleWaitThread (wasm://wasm/01b05c4e:1:1554611)
    at rts_evalLazyIO (wasm://wasm/01b05c4e:1:1499817)
    at hs_main (wasm://wasm/01b05c4e:1:1510641)
    at main (wasm://wasm/01b05c4e:1:166036)
*** unexpected failure for T4221(normal)

It's very likely hitting the internal limits about libffi-wasm. And I don't intend to bump limits to mitigate the failures here, the way forward would really be #22590.