scripts: make security checks architecture independent

Summary:

script: remove gitian reference from symbol-check.py

https://github.com/bitcoin/bitcoin/pull/22405/commits/797b3ed9090030f32fade81803b580562d4a90a3

Note that this is the only relevant commit from core#22405, everything else was backported with guix.

core#23811

scripts: match on EXE_FORMATS rather than name string

This is a minor change, but matching on the EXE_FORMAT is slightly simpler and more robust.

It also fixes the etype == lief.EXE_FORMATS.UNKNOWN check in both python scripts.

core#23838

scripts: make security checks architecture independent

This paves the way for using and checking for architecture dependent
flags like -fcf-protection on x86_64 Linux and -mbranch-protection on 64
bit ARM.

This is a backport of core#23811 and core#23838

Test Plan: guix build and gitian builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14007