Fix build failure when libcloudproviders dependency is unavailable

[ckamm]

Error:

CMake Error at cmake/modules/FindLibcloudproviders.cmake:27 (if):
  if given arguments:
    "(" "EQUAL" "0" ")" "AND" "(" "LESS" "3" ")"
Unknown arguments specified

Due to insufficient escapes in the regex used.

[ckamm]

QA: This is one of these issues that I normally wouldn't even have created. To test, check that cmake doesn't error when the environment doesn't have libcloudproviders. The automated builders will verify that.

[guruz]

Is this related?
https://build.opensuse.org/public/build/isv:ownCloud:desktop:daily:2.6/Ubuntu_18.10/x86_64/owncloud-client/_log

 173s] -- Added vfsPlugin without tests: suffix
[  173s] Can't determine libcloudproviders version, not enabling it
[  173s] -- Could NOT find LIBCLOUDPROVIDERS (missing: LIBCLOUDPROVIDERS_LIBRARY LIBCLOUDPROVIDERS_INCLUDE_DIR) 
[  173s] CMake Error at /usr/share/cmake-3.12/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
[  173s]   Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)
[  173s] Call Stack (most recent call first):
[  173s]   /usr/share/cmake-3.12/Modules/FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
[  173s]   /usr/share/cmake-3.12/Modules/FindPkgConfig.cmake:39 (find_package_handle_standard_args)
[  173s]   src/gui/libcloudproviders/libcloudproviders.cmake:2 (find_package)
[  173s]   src/gui/CMakeLists.txt:320 (include)
[  173s] 
[  173s] 
[  173s] -- Configuring incomplete, errors occurred!

https://build.opensuse.org/project/show/isv:ownCloud:desktop:daily:2.6

[ckamm]

Not related, but another failure when the environment doesn't have pkgconfig. Will fix and make a new ticket.

[jnweiger]

Linux packages have no support for libcloudproviders currently. If that feature is meant for milestone 2.6.0 then we have a blocker.

• Ubuntu 18.04 and before: libcloudproviders does not exist.
• Ubuntu 18.10: libcloudproviders 0.2.5 is too old. We need 0.30
• Ubuntu 19.04: libcloudproviders 0.3.0

[jnweiger]

Tested in obs:

The build log now says

[  160s] -- Added vfsPlugin without tests: suffix
[  160s] -- Found LIBCLOUDPROVIDERS: /usr/lib/x86_64-linux-gnu/libcloudproviders.so  
[  160s] -- Checking for one of the modules 'gio-2.0'
[  160s] Building with libcloudproviders
[  160s] -- Could NOT find ECM (missing: ECM_DIR)
....
[  341s] make[3]: Entering directory '/usr/src/packages/BUILD/obj-x86_64-linux-gnu'
[  341s] [ 33%] Building CXX object src/gui/CMakeFiles/owncloud.dir/main.cpp.o
[  341s] cd /usr/src/packages/BUILD/obj-x86_64-linux-gnu/src/gui && /usr/bin/c++  -DQT_CONCURRENT_LIB -DQT_CORE_LIB -DQT_DBUS_LIB -DQT_DEPRECATED_WARNINGS -DQT_DISABLE_DEPRECATED_BEFORE=0 -DQT_GUI_LIB -DQT_MESSAGELOGCONTEXT -DQT_NETWORK_LIB -DQT_NO_DEBUG -DQT_USE_QSTRINGBUILDER -DQT_WIDGETS_LIB -DQT_XML_LIB -DUNICODE -DUSE_FDO_NOTIFICATIONS -DWITH_LIBCLOUDPROVIDERS -D_UNICODE -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu/src/gui/owncloud_autogen/include -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu -I/usr/src/packages/BUILD/src -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu/src -I/opt/ownCloud/qt-5.12.2/include/qt5keychain -I/usr/src/packages/BUILD/src/3rdparty/QProgressIndicator -I/usr/src/packages/BUILD/src/3rdparty/qtlockedfile -I/usr/src/packages/BUILD/src/3rdparty/qtsingleapplication -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu/src/gui -I/usr/src/packages/BUILD/src/libsync -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu/src/libsync -I/usr/src/packages/BUILD/obj-x86_64-linux-gnu/src/csync -I/usr/src/packages/BUILD/src/csync -I/usr/src/packages/BUILD/src/csync/std -I/usr/src/packages/BUILD/src/gui -isystem /usr/include/libmount -isystem /usr/include/blkid -isystem /usr/include/uuid -isystem /usr/include/glib-2.0 -isystem /usr/lib/x86_64-linux-gnu/glib-2.0/include -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5 -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtWidgets -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtGui -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtCore -isystem /usr/../opt/ownCloud/qt-5.12.2/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++-64 -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtNetwork -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtXml -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtConcurrent -isystem /opt/ownCloud/qt-5.12.2/include/x86_64-linux-gnu/qt5/QtDBus  -g -O2 -fdebug-prefix-map=/usr/src/packages/BUILD=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -Wall -Wextra -pedantic -Wno-long-long -Wno-gnu-zero-variadic-macro-arguments -Wpedantic -fPIE   -fPIC -std=gnu++14 -o CMakeFiles/owncloud.dir/main.cpp.o -c /usr/src/packages/BUILD/src/gui/main.cpp

Reference #7209
We cannot test that any further, as all linux distros have that feature still disabled in their gnome/gtk
Good enough to verify the issue was addressed. If there is more we can test, please re-open.