Update linuxclientinstall.sh to support ubuntu aarch64

[carefreepineapple]

adding support for ubuntu aarch64 installation.

[carefreepineapple]

There does seem to be an issue installing the aarch64 deb file, but i'm not sure if it has to do with the installer or the deb file.

N: Download is performed unsandboxed as root as file '/home/ubuntu/rustdesk-1.2.1-aarch64.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: No such file or directory (os error 2)', src/core_main.rs:241:76
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
./rust.sh: line 82:  3708 Aborted                 (core dumped) rustdesk --password ${admintoken}

If you run the installer a second time, it works without issue.

[carefreepineapple]

I hate adding sleeps, but after testing it became clear that the package manager was not finished with installation before trying to launch the rustdesk executable, causing failures when accessing dependencies that were not yet available.

Maybe someone else has a better idea.

oh and relative paths are evil.

[dinger1986]

I have no way to test this at the moment so if you are happy I can accept the PR?

[carefreepineapple]

@dinger1986 i'm happy with it if it looks good to you.

[dinger1986]

Looks fine from the look I could get over it via my phone! Should be fine I am sure