Fix CMake build on macOS (don't try to link against Qt's X11Extras) (#267)

macOS is identified as UNIX by CMake, but Qt doesn't actually use X11
there (and X11 support is not available by default anyway). Change the
condition that includes X11Extras to if (UNIX AND NOT APPLE) instead of
just if (UNIX) to mitigate that. This makes the build on macOS work
with CMake.

Co-authored-by: Christian Seiler <c.seiler@luxflux.de>

Author: chris-se

adsConfig.cmake

@@ -2,5 +2,7 @@ include(CMakeFindDependencyMacro)
 find_dependency(Qt5Core ${REQUIRED_QT_VERSION} REQUIRED)
 find_dependency(Qt5Gui ${REQUIRED_QT_VERSION} REQUIRED)
 find_dependency(Qt5Widgets ${REQUIRED_QT_VERSION} REQUIRED)
-find_dependency(Qt5X11Extras ${REQUIRED_QT_VERSION} REQUIRED)
+if(UNIX AND NOT APPLE)
+    find_dependency(Qt5X11Extras ${REQUIRED_QT_VERSION} REQUIRED)
+endif()
 include("${CMAKE_CURRENT_LIST_DIR}/adsTargets.cmake")

src/CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.5)
 project(QtAdvancedDockingSystem LANGUAGES CXX VERSION ${VERSION_SHORT})
 find_package(Qt5 5.5 COMPONENTS Core Gui Widgets REQUIRED)
-if (UNIX)
+if (UNIX AND NOT APPLE)
 	find_package(Qt5 5.5 COMPONENTS X11Extras REQUIRED)
 endif()
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
@@ -48,7 +48,7 @@ set(ads_HEADERS
     IconProvider.h
     DockComponentsFactory.h
 )
-if (UNIX)
+if (UNIX AND NOT APPLE)
     set(ads_SRCS linux/FloatingWidgetTitleBar.cpp ${ads_SRCS})
     set(ads_HEADERS linux/FloatingWidgetTitleBar.h ${ads_HEADERS})
 endif()
@@ -60,7 +60,7 @@ else()
     target_compile_definitions(qtadvanceddocking PRIVATE ADS_SHARED_EXPORT)
 endif()
 target_link_libraries(qtadvanceddocking PUBLIC Qt5::Core Qt5::Gui Qt5::Widgets)
-if (UNIX)
+if (UNIX AND NOT APPLE)
     target_link_libraries(qtadvanceddocking PUBLIC Qt5::X11Extras)
 endif()
 set_target_properties(qtadvanceddocking PROPERTIES