Just setting the field android-extra-plugins to an empty string resulted
in androiddeployqt complaining about
"External resource  does not exist or not a correct directory!"
so the field is completely left out now if no plugin data dirs are found.
For consistency the same is done with the android-extra-libs field.

REVIEW: 127700
BUG: 362578

Thanks apol for review

Better wait a little until applying this change, since this might break
assumptions, and we don't know yet if all distros are using a recent enough
AppStream (Generator) release.

This reverts commit 4b7a90bfe7a3e2eb3ae83c946c182a79fabc51e3.

As per AppStream release 0.9.4

Make Qt and ECM-based projects use the same directory sctructure (i.e.
where plugins are, libs, etc.) by default. Otherwise it creates a tiny mess
that might be controlled but usually won't.

In the end, otherwise, people need to keep adapting their systems with
environment variables anyway. All distros end up setting always this
setting as ON, as well as brave developers who don't have separate prefixes
for Qt and KDE.

REVIEW: 127169

If one subdir in the project includes this file, all others can use the function
but they don't see the value of the variable, which leads to a strange error

CMake Error at ECM/modules/ECMQtDeclareLoggingCategory.cmake:114 (configure_file):
  configure_file input location <srcdir> is a directory but a file was expected.

Happened in KIO, with kio/gui doing include+function call, and then adding
function call in kio/widgets.

REVIEW: 127432

Clang automatically adds its runtime library (librt) when given the
-fsanitize options. Do not force the GCC runtime libraries (asan, tsan,
lsan), this results in "Your application is linked against incompatible
ASan runtimes." errors when using the library in an executable built
using Clang.

Acked by Mathieu Tarral

REVIEW: 127513

Use the CMAKE_INSTALL_PREFIX to ensure that only a file in the install
location will be touched.  Otherwise a user running

 make install

as root would create root-owned files in the build directory.

Use the cmake -E touch command to update the mtime of the directory.
That command exists since late 2007, but this manual file creation
workaround pre-dates that by a few months (kdelibs SVN revision 691973).

There is no chance any calling code is already passing an absolute path
here because later in the function it is already used together with a
CMAKE_INSTALL_PREFIX.

Inspired-by: REVIEW 127445

This reverts commit 1d4bc35cf9383177459544d6fcd9de35edf3e77d.

QLoggingCategory has always included QDebug, so this has always been
superfluous.