set project cpp-files to c++17 when qt is included, search and link to a threading library

src/CMakeLists.txt

@@ -130,6 +130,9 @@ if(APPLE)
 endif()
 
 if(QT)
+  set(CMAKE_CXX_STANDARD 17)
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  set(CMAKE_CXX_EXTENSIONS OFF)
   find_package(Qt5 COMPONENTS Core Widgets REQUIRED)
 endif()
 
@@ -249,4 +252,4 @@ elseif(WIN32)
 	add_subdirectory(win)
 else()
 	add_subdirectory(unix)
-endif()
+endif()

src/qt/CMakeLists.txt

@@ -4,6 +4,8 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)
 set(CMAKE_AUTORCC ON)
 
+find_package(Threads REQUIRED)
+
 add_library(plat STATIC qt.c qt_main.cpp qt_platform.cpp qt_midi.cpp cpp11_thread.cpp)
 add_library(ui STATIC
     qt_ui.cpp
@@ -78,10 +80,12 @@ target_link_libraries(
     plat
     PRIVATE
     Qt5::Widgets
+    Threads::Threads
 )
 
 target_link_libraries(
     ui
     PRIVATE
     Qt5::Widgets
+    Threads::Threads
 )