Will CMake properly detect both debug and release libs if cmake files are in separate directories?

sorry can"t answer your question, because of lack of knowledge.

I can send you the build log of the compilation on my linux Fedora 23 machine, maybe it
brings more light into the dark ?
vlc-qt-build-messages.txt

This is helpful. Can you also provide spec file. I can add it to the repo.

Of course, if I can help with it.
At the moment I"am working on a review of the vlc-qt package for the Fedora rpmfusion repo.
It"s not yet complete and it can even tiling changes
https://bugzilla.rpmfusion.org/show_bug.cgi?id=3963

Spec URL: https://martinkg.fedorapeople.org/Review/SPECS/vlc-qt.spec
SRPM URL: https://martinkg.fedorapeople.org/Review/SRPMS/vlc-qt-1.0.0-1.fc23.src.rpm

hopefully you can add the libsuffix patch to your github

I supported GNUInstallDirs. Please check if this works for you as expected. Otherwise I will just use your patch.

i checked out your version from git.
the libraries will be installed correctly under /usr/lib64/
but the *.cmake files are still leaves under /usr/lib

Directory not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib64/cmake/VLCQt
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib64/cmake/VLCQt/VLCQt*.cmake

[martin@fc23 SPECS]$ ll /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib64/
libVLCQtCore.so libVLCQtCore.so.1.0.0 libVLCQtQml.so.1.0 libVLCQtWidgets.so libVLCQtWidgets.so.1.0.0
libVLCQtCore.so.1.0 libVLCQtQml.so libVLCQtQml.so.1.0.0 libVLCQtWidgets.so.1.0 pkgconfig/
[martin@fc23 SPECS]$ ll /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib64/
total 340
lrwxrwxrwx 1 martin martin 19 Feb 7 17:58 libVLCQtCore.so -> libVLCQtCore.so.1.0
lrwxrwxrwx 1 martin martin 21 Feb 7 17:58 libVLCQtCore.so.1.0 -> libVLCQtCore.so.1.0.0
-rwxr-xr-x 1 martin martin 175280 Feb 7 17:58 libVLCQtCore.so.1.0.0
lrwxrwxrwx 1 martin martin 18 Feb 7 17:58 libVLCQtQml.so -> libVLCQtQml.so.1.0
lrwxrwxrwx 1 martin martin 20 Feb 7 17:58 libVLCQtQml.so.1.0 -> libVLCQtQml.so.1.0.0
-rwxr-xr-x 1 martin martin 72696 Feb 7 17:58 libVLCQtQml.so.1.0.0
lrwxrwxrwx 1 martin martin 22 Feb 7 17:58 libVLCQtWidgets.so -> libVLCQtWidgets.so.1.0
lrwxrwxrwx 1 martin martin 24 Feb 7 17:58 libVLCQtWidgets.so.1.0 -> libVLCQtWidgets.so.1.0.0
-rwxr-xr-x 1 martin martin 93256 Feb 7 17:58 libVLCQtWidgets.so.1.0.0
drwxr-xr-x 2 martin martin 4096 Feb 7 17:58 pkgconfig
[martin@fc23 SPECS]$ ll /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib/cmake/VLCQt*
/home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib/cmake/VLCQt:
total 8
-rw-r--r-- 1 martin martin 1469 Feb 7 10:49 VLCQtConfig.cmake
-rw-r--r-- 1 martin martin 1269 Feb 7 17:57 VLCQtConfigVersion.cmake

/home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib/cmake/VLCQtCore:
total 16
-rw-r--r-- 1 martin martin 364 Feb 7 10:49 VLCQtCoreConfig.cmake
-rw-r--r-- 1 martin martin 1269 Feb 7 17:57 VLCQtCoreConfigVersion.cmake
-rw-r--r-- 1 martin martin 806 Feb 7 17:57 VLCQtCoreTargets-noconfig.cmake
-rw-r--r-- 1 martin martin 3468 Feb 7 17:57 VLCQtCoreTargets.cmake

/home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib/cmake/VLCQtQml:
total 16
-rw-r--r-- 1 martin martin 507 Feb 7 10:49 VLCQtQmlConfig.cmake
-rw-r--r-- 1 martin martin 1269 Feb 7 17:57 VLCQtQmlConfigVersion.cmake
-rw-r--r-- 1 martin martin 798 Feb 7 17:57 VLCQtQmlTargets-noconfig.cmake
-rw-r--r-- 1 martin martin 3461 Feb 7 17:57 VLCQtQmlTargets.cmake

/home/martin/rpmbuild/BUILDROOT/vlc-qt-1.0.1-1.fc23.x86_64/usr/lib/cmake/VLCQtWidgets:
total 16
-rw-r--r-- 1 martin martin 539 Feb 7 10:49 VLCQtWidgetsConfig.cmake
-rw-r--r-- 1 martin martin 1269 Feb 7 17:57 VLCQtWidgetsConfigVersion.cmake
-rw-r--r-- 1 martin martin 830 Feb 7 17:57 VLCQtWidgetsTargets-noconfig.cmake
-rw-r--r-- 1 martin martin 3489 Feb 7 17:57 VLCQtWidgetsTargets.cmake

Just to make sure, did you build feature/gnuinstalldirs branch?

I think I"m wrong, i checked out:
https://github.com/vlc-qt/vlc-qt/archive/cf4a655722e4313f3b1476fe33804c769bb9a8b9
and
https://github.com/vlc-qt/vlc-qt/archive/b46ef0747ddc1c9c3b442acbd24b63785584c7c8
but both builds fails.

Interesting that it works for libraries but not for CMake files. I will add your original patch for now and leave this for later as it needs more investigation.

Your patch should be in devel branch. If that"s OK for now, I"ll release 1.0.1 with it in today or tomorrow (as I will also be updating to VLC 2.2.2).

That"s ok, many thanks for supporting me.

@martinkg Could you please check the latest version feature/gnuinstalldirs branch again.

i testet with the last git checkout, but the libraries are installed into /usr/lib, correct is /usr/lib64

RPM build errors:
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/libVLCQt_.so._
Directory not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/cmake/VLCQt
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/cmake/VLCQt/VLCQt*.cmake
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/qml/VLCQt/libVLCQt.so
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/qml/VLCQt/libVLCQt.so.1.1
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/qml/VLCQt/libVLCQt.so.1.1.0
File not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/qml/VLCQt/qmldir
Directory not found: /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib64/qml/VLCQt
[martin@fc24 SPECS]$

[martin@fc24 SPECS]$ ll /home/martin/rpmbuild/BUILDROOT/vlc-qt-1.1.0-0.1git98a0b9a.fc24.x86_64/usr/lib/
total 528
drwxr-xr-x 6 martin martin 4096 Aug 12 10:38 cmake
drwxr-xr-x 5 martin martin 4096 Aug 12 10:38 debug
lrwxrwxrwx 1 martin martin 19 Aug 12 10:38 libVLCQtCore.so -> libVLCQtCore.so.1.1
lrwxrwxrwx 1 martin martin 21 Aug 12 10:38 libVLCQtCore.so.1.1 -> libVLCQtCore.so.1.1.0
-rwxr-xr-x 1 martin martin 249208 Aug 12 10:38 libVLCQtCore.so.1.1.0
lrwxrwxrwx 1 martin martin 18 Aug 12 10:38 libVLCQtQml.so -> libVLCQtQml.so.1.1
lrwxrwxrwx 1 martin martin 20 Aug 12 10:38 libVLCQtQml.so.1.1 -> libVLCQtQml.so.1.1.0
-rwxr-xr-x 1 martin martin 175296 Aug 12 10:38 libVLCQtQml.so.1.1.0
lrwxrwxrwx 1 martin martin 22 Aug 12 10:38 libVLCQtWidgets.so -> libVLCQtWidgets.so.1.1
lrwxrwxrwx 1 martin martin 24 Aug 12 10:38 libVLCQtWidgets.so.1.1 -> libVLCQtWidgets.so.1.1.0
-rwxr-xr-x 1 martin martin 101552 Aug 12 10:38 libVLCQtWidgets.so.1.1.0
drwxr-xr-x 2 martin martin 4096 Aug 12 10:38 pkgconfig

May it be related with this? It works for me in Ubuntu.

@martinkg try one more time. It seems I need to include GNUInstallDirs after project call. If this doesn"t fix your build, I will set up a Fedora virtual machine :)

I managed to fix the spec. It builds for me on Fedora 24 and seems OK. I will merge this into 1.1.1 as it also fixes Ubuntu location. Please test, when you can.
Change build to:

%build
%cmake . \
    -DSYSTEM_QML:BOOL=ON \
    -DCMAKE_INSTALL_LIBDIR:PATH=%{_libdir}
make %{?_smp_mflags}

Change files to:

%files
%license LICENSE.md
%doc README.md
%{_qt5_libdir}/libVLCQt*.so.*
%dir %{_qt5_libdir}/cmake/VLCQt/
%{_qt5_libdir}/cmake/VLCQt/VLCQt*.cmake
%{_qt5_libdir}/qt5/qml/VLCQt/libVLCQt.so
%{_qt5_libdir}/qt5/qml/VLCQt/libVLCQt.so.1.1
%{_qt5_libdir}/qt5/qml/VLCQt/libVLCQt.so.1.1.0
%{_qt5_libdir}/qt5/qml/VLCQt/qmldir
%dir %{_qt5_libdir}/qt5/qml/VLCQt/

Build with latest feature/gnuinstalldirs branch