This is a slightly modernized version of Pino's original implementation
found in KF5 and Plasma.

We have identical copies of this in kinit, kwin, ksysguard and
powerdevil. This makes it a natural candidate for inclusion in ECM.

It is based on the one that can be found in KWin.

Several KDE projects already use libepoxy (KWin and KDeclarative).

When creating a library or executable, several source files are combined
into a binary artifact that has an outbound license of its own. This test
generator allows to check if the combined source files are compatible
with the desired outbound license.

Requirements for using these tests:
- input source files must contain the SPDX-License-Information tag
- python3 must be available
- the "reuse spdx" tool must be available

An intended use case is to generate client-side and server-side code for
protocols shipped in the wayland-protocols package with qtwaylandscanner.

Summary:
It serves as a replacement for `kdbusaddons_generate_dbus_service_file`.

An application can be a DBus-activated service just fine without using KDBusAddons.
Moreover, this new module uses named arguments for future-proofing, and adds support for specifying a `SystemdService`.
It also cleans up the confusion on what the "path" is about: Rather than requiring to specify executable and path separately, we just extract the executable file name on Windows, if necessary.

Usage:
```
ecm_generate_dbus_service_file(NAME org.kde.kded5
                               EXECUTABLE ${KDE_INSTALL_FULL_BINDIR}/kded5
                               SYSTEMD_SERVICE plasma-kded)
```

Test Plan:
* Was able to generate a kded service file
* Was able to generate a kded service file with `SystemdUnit`
* Verified that it moaned when executable wasn't an absolute path
* Untested on Windwos

Reviewers: #frameworks, davidedmundson, kossebau, kfunk, habacker

Subscribers: kde-frameworks-devel, kde-buildsystem

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D29051

Summary:
This, as the name suggests, configures a file and installs it.

It's not very complicated but it's a repeated pattern in plasma that
gets quite messy dealing with temporary files.

Test Plan: Used in a project

Reviewers: #build_system

Subscribers: apol, kossebau, pino, kde-frameworks-devel, kde-buildsystem

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D28355