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.

Author: hedrok

scripts/package-build/strongswan/package.toml

@@ -3,8 +3,14 @@ name = "strongswan"
 commit_id = "debian/5.9.11-2"
 scm_url = "https://salsa.debian.org/debian/strongswan.git"
 
+# systemd now contains pkg-config files and systemd-dev is not needed
+# this changes debian/control so the change is needed before mk-build-deps
+# call so cannot be included in normal patches
+pre_build_hook = "sed -i '/ systemd-dev /d' debian/control"
+
 # build_cmd = "cd ..; yes | ./build.sh; ./build-vici.sh"
 build_cmd = """
+set -e
 export DEBEMAIL="maintainers@vyos.net"
 export DEBFULLNAME="VyOS Package Maintainers"