Add -Wnon-virtual-dtor and resolve issues

The IPolicyConfig file is a third party file and since it describes a
third party API we can't make changes to it. Adding it via the system
includes disables warnings on most compilers.

build_scripts/qt/compilers/clang-msvc.pri

@@ -11,3 +11,5 @@ QMAKE_CXXFLAGS += /std:c++17
 QMAKE_CXXFLAGS += -Xclang -Wshadow
 
 QMAKE_CXXFLAGS += -Wold-style-cast
+
+QMAKE_CXXFLAGS += -Wnon-virtual-dtor

build_scripts/qt/compilers/clang.pri

@@ -5,3 +5,5 @@ QMAKE_CXXFLAGS += --system-header-prefix=third-party
 QMAKE_CXXFLAGS += -Wshadow
 
 QMAKE_CXXFLAGS += -Wold-style-cast
+
+QMAKE_CXXFLAGS += -Wnon-virtual-dtor

build_scripts/qt/compilers/gcc.pri

@@ -6,3 +6,5 @@ QMAKE_CXXFLAGS += -Werror
 QMAKE_CXXFLAGS += -Wshadow
 
 QMAKE_CXXFLAGS += -Wold-style-cast
+
+QMAKE_CXXFLAGS += -Wnon-virtual-dtor

build_scripts/qt/sources.pri

@@ -43,18 +43,19 @@ win32 {
     SOURCES += src/tabcontrollers/audiomanager/AudioManagerWindows.cpp \
         src/tabcontrollers/keyboardinput/KeyboardInputWindows.cpp
     HEADERS += src/tabcontrollers/audiomanager/AudioManagerWindows.h \
-                src/tabcontrollers/audiomanager/IPolicyConfig.h \
         src/tabcontrollers/keyboardinput/KeyboardInputWindows.h
 }
 
 win32-msvc {
     INCLUDEPATH += third-party/openvr/headers \
-                            third-party/easylogging++
+                    third-party/easylogging++ \
+                    third-party/policyconfig
 }
 
 win32-clang-msvc {
     QMAKE_CXXFLAGS += /imsvc "$$PWD/../../third-party/openvr/headers"
     QMAKE_CXXFLAGS += /imsvc "$$PWD/../../third-party/easylogging++"
+    QMAKE_CXXFLAGS += /imsvc "$$PWD/../../third-party/policyconfig"
 }
 
 # Anything g++ or clang

src/tabcontrollers/audiomanager/AudioManagerWindows.h

@@ -5,7 +5,7 @@
 #include <mmdeviceapi.h>
 #include <functiondiscoverykeys_devpkey.h>
 #include <endpointvolume.h>
-#include "IPolicyConfig.h"
+#include <IPolicyConfig.h>
 #include <mutex>
 
 // application namespace