VOR demod: compile only if prerequisites are available. Fixes #727

plugins/channelrx/CMakeLists.txt

@@ -2,6 +2,7 @@ project(demod)
 
 if (Qt5Quick_FOUND AND Qt5QuickWidgets_FOUND AND Qt5Positioning_FOUND)
     add_subdirectory(demodadsb)
+    add_subdirectory(demodvor)
 endif()
 add_subdirectory(demodam)
 add_subdirectory(demodbfm)
@@ -13,7 +14,6 @@ add_subdirectory(localsink)
 add_subdirectory(filesink)
 add_subdirectory(freqtracker)
 add_subdirectory(demodchirpchat)
-add_subdirectory(demodvor)
 
 if(LIBDSDCC_FOUND AND LIBMBE_FOUND)
     add_subdirectory(demoddsd)