[clang] [llvm] Revert changes in AddDefaultGCCPrefixes() for SystemZTriples. (PR #94729)

[Ilya Leoshkevich via llvm-commits]

iii-i wrote:

This is still failing for me on Debian. The problem seems to be that `/etc/lsb-release` does not exist. There are
```
# cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux bookworm/sid"
NAME="Debian GNU/Linux"
VERSION_CODENAME=bookworm
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"
```
and
```
# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux bookworm/sid
Release:        n/a
Codename:       bookworm
```
though. Would it make sense to include both of them in the check?

https://github.com/llvm/llvm-project/pull/94729