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GH-34784: [Go] Fix 32-bit build (#35767)



### Rationale for this change
Two locations in the code cause issues when building with `GOARCH=386` (e.g. 32-bit systems).

### What changes are included in this PR?
In the `compute` package we assume a 64-bit system when using an untyped `int` to hold `math.MaxInt64` which overflows on a 32-bit system. So we just explicitly identify it as an `int64`

In the `cdata` package we use the older `*(*[maxlen]*C.void)(unsafe.Pointer(.....))[:]` syntax to retrieve the `void**` for the buffers, with maxlen set to a very large constant. Unfortunately on a 32-bit system this is larger than the address space. Instead we switch to using the `unsafe.Slice` method that was added in go1.17.

* Closes: #34784

Authored-by: Matt Topol <zotthewizard@gmail.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>