T8099: Fix strongswan build

* Remove systemd-dev from dependencies
* Add `set -e` to build_cmd.

Strongswan depends on `systemd` and `systemd-dev`, installing both fails with:

```
The following packages have unmet dependencies:
 systemd-dev : Breaks: systemd (< 253-2~) but 252.39-1~deb12u2 is to be installed
E: Unable to correct problems, you have held broken packages.
```

`systemd-dev` contains pkg-config files for systemd and udev, but
current `systemd` package installs identical
`/usr/share/pkgconfig/systemd.pc` - maybe that's why packages cannot be
installed simultaneously.

So remove it from dependencies.

Though the package failed to build, `./build.py` returned 0 as
`build_cmd` has two build commands one after another without any checks
of exit value of first one that builds strongswan. Added `set -e` so
that any failure in any of commands results to build failure.

0 files changed, 0 insertions, 0 deletions