Deno: "deno upgrade" downloads the `x86_64` binary release on aarch64

[06kellyjac]

Until aarch64 releases are vendored (#4862), deno upgrade should exit with an error message rather than downloading, unzipping, and trying to execute an x86_64 binary on an aarch64 system.

[ry]

I agree and should be an easy fix

[06kellyjac]

Error log:

> ./target/debug/deno upgrade -f --dry-run -L debug
Checking for latest version
starting new connection: https://github.com/
resolving host="github.com"
...
Version has been found
Deno is upgrading to version 1.0.0
downloading https://github.com/denoland/deno/releases/download/v1.0.0/deno-x86_64-unknown-linux-gnu.zip
...
incoming body completed
pooling idle connection for ("https", github-production-release-asset-2e65be.s3.amazonaws.com)
Archive:  /run/user/1000/.tmp0Ap59Q/deno.zip
  inflating: deno
error: Exec format error (os error 8)

> file /run/user/1000/.tmp0Ap59Q/deno
/run/user/1000/.tmp0Ap59Q/deno: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=b914ea3fdbf0a4300975e7f314d7e7d8d7f44c2a, with debug_info, not stripped

> uname -mo
aarch64 GNU/Linux

[06kellyjac]

Forked deno, starting work on the fix