fix: Use dpkg instead uname to get unified arch in postinst debian script

[kayano]

It seems uname changed what it returns doing uname -m.
I'm getting aarch64 running uname -m which results in wrong binary being installed when using nethermind ppa on arm64 machine.

Changes

• use dpkg instead uname in ppa postinst debian script

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Ubuntu packaging

Testing

Requires testing

• Yes
• No

[rubo]

What OS does return aarch instead of arm?

[kayano]

What OS does return aarch instead of arm?

lsb_release -a

No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.4 LTS
Release:	22.04
Codename:	jammy

uname -a
Linux  6.5.0-1018-aws #18~22.04.1-Ubuntu SMP Fri Apr  5 17:56:39 UTC 2024 aarch64 aarch64 aarch64 GNU/Linux

[rubo]

Good catch. We'll improve the script further to check the architectures explicitly and exit if not supported instead of falling back to the wrong one. Thank you for your contribution.