Tools: [skip ci] allow to build plugin as a top-level project

src/Tools/plugins/widget/CMakeLists.txt

@@ -1,11 +1,17 @@
-project(FreeCAD_widgets)
-cmake_minimum_required(VERSION 3.2.0)
+if (PROJECT_NAME)
+    set(IS_SUB_PROJECT TRUE)
+endif()
 
-#set(CMAKE_INCLUDE_CURRENT_DIR ON)
-#set(CMAKE_AUTOMOC ON)
+if (NOT IS_SUB_PROJECT)
+    project(FreeCAD_widgets)
+    cmake_minimum_required(VERSION 3.2.0)
 
-#find_package(Qt5Widgets REQUIRED)
-#find_package(Qt5Designer REQUIRED)
+    set(CMAKE_INCLUDE_CURRENT_DIR ON)
+    set(CMAKE_AUTOMOC ON)
+
+    find_package(Qt5Widgets REQUIRED)
+    find_package(Qt5Designer REQUIRED)
+endif()
 
 include_directories(
     ${Qt5Core_INCLUDE_DIRS}
@@ -48,17 +54,19 @@ endif()
 
 target_link_libraries(FreeCAD_widgets PRIVATE ${Qt5Widgets_LIBRARIES} ${Qt5Designer_LIBRARIES})
 target_compile_options(FreeCAD_widgets PRIVATE ${COMPILE_OPTIONS})
-set (libFreeCAD_widgets "libFreeCAD_widgets"  PARENT_SCOPE)
 
 
 # Get the install location of a plugin to determine the path to designer plguins
 get_target_property(QMAKE_EXECUTABLE Qt5::qmake LOCATION)
 exec_program(${QMAKE_EXECUTABLE} ARGS "-query QT_INSTALL_PLUGINS" RETURN_VALUE return_code OUTPUT_VARIABLE DEFAULT_QT_PLUGINS_DIR )
 set(DESIGNER_PLUGIN_LOCATION ${DEFAULT_QT_PLUGINS_DIR}/designer CACHE FILEPATH "Path where the plugin will be installed to")
-#message(STATUS "Plugin will be installed to: ${DESIGNER_PLUGIN_LOCATION}")
 
-# Override the CMake variable
-#set(CMAKE_INSTALL_PREFIX ${DESIGNER_PLUGIN_LOCATION} CACHE PATH "Install path to Qt Designer plugins" FORCE)
+if (NOT IS_SUB_PROJECT)
+    message(STATUS "Plugin will be installed to: ${DESIGNER_PLUGIN_LOCATION}")
+else()
+    set (libFreeCAD_widgets "${CMAKE_SHARED_LIBRARY_PREFIX}FreeCAD_widgets${CMAKE_SHARED_LIBRARY_SUFFIX}" PARENT_SCOPE)
+endif()
+
 
 INSTALL(TARGETS FreeCAD_widgets
     LIBRARY DESTINATION "$ENV{DESTDIR}${DESIGNER_PLUGIN_LOCATION}"