CMake >= 3.0 supports bracket comments, and the reStructuredText
integration code in sphinx/ext/ecm.py already supports extracting
the docs from a bracket comment instead.
Editing documentation without leading line comment markers is more simple,
e,g. when reflowing text over lines.

With ECM meanwhile requiring CMake 3.5 now it is possible to switch
(and thus follow also the approach used by cmake itself).

NO_CHANGELOG

If we tell the compiler to link the runtime statically and then explicitly link
the dynamic runtime and prohibit the static we continue to produce dynamic
builds...

This matches most of the existing code in KDE; also note that Qt has the
same setting (also stating in a comment in their _clang-format that this
matching their existing code).

To prevent cmake errors with exiting usages it is checked if the target already exists.

When building multiple KDE projects, installing them to "$DESTDIR"
and having cmake look for kde dependencies in "$DESTDIR" using
"CMAKE_PREFIX_PATH=$DESTDIR/usr", we currently get failures when
calling find_package() on projects that use KDE_INSTALL_QTPLUGINDIR,
KDE_INSTALL_QTQMLDIR and KDE_INSTALL_QTQUICKIMPORTSDIR because these
are defined as absolute paths when KDE_INSTALL_USE_QT_SYS_PATHS is
enabled.

This commit defines these paths relative to qmake's QT_INSTALL_PREFIX
property instead when KDE is install to the same prefix as Qt. This
fixes DESTDIR installations because with relative paths, CMake will
search for these paths in "$DESTDIR" as well as "/".

We limit this change to the scenario where the Qt and CMake install
prefixes are the same because always doing this would break backwards
compatibility as qml and plugins would be installed into CMAKE_INSTALL_PREFIX
instead of QT_INSTALL_PREFIX after this change.

The --sort=name option was only added in version 1.28
which isn't available in Centos 7 yet e.g.