Unable to build on AArch64

[tom91136]

On AArch64 Linux, I'm observing the same failure as extendr/extendr#628.
I believe upgrading the extendr dependency from the pinned one (ref to extendr/extendr#627) to extendr/extendr#629 will resolve this as the fix was introduced in that PR.
Alternatively, we can probably use rev = "v0.6.0" which was released last October and appears to be stable.

[shrektan]

Thanks. PR is welcomed.