Fix the Linux build of the qt6 branch, compile QML to bytecode only

- Remove Core5Compat (unused, not part of the Steam Frame's system Qt).
- Request GuiPrivate explicitly (required since Qt 6.10 for QRhi); temporary
  until rendering moves to public API.
- Compile QML to bytecode only: C++ generated from QML uses private Qt API
  that only matches the exact Qt version it was built with.
- Pick the OpenVR library per architecture (linux64, linuxarm64, win64) for
  linking and for the copy next to the binary; RPATH $ORIGIN.
- Link libXtst, needed by input_sender_X11.cpp.
- Include d3d11.h and handle QRhi::D3D11 only on Windows.
- Replace leftover easylogging LOG(INFO) calls with qInfo().

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/overlaycontroller.cpp

@@ -30,7 +30,10 @@
 #include <qnamespace.h>
 #include <rhi/qrhi.h>
 #include <stdexcept>
-#include <d3d11.h>
+// Direct3D exists only on Windows.
+#ifdef _WIN32
+#    include <d3d11.h>
+#endif
 
 // application namespace
 namespace advsettings
@@ -521,21 +524,25 @@ void OverlayController::SetWidget( QQuickItem* quickItem,
         auto ctrlRole = info.second;
         if ( vr::TrackedDeviceClass_HMD == ctrlRole )
         {
-            LOG(INFO) << "HMD is: " << ovr_system_wrapper::getDeviceName(device);
+            qInfo() << "HMD is: "
+                    << ovr_system_wrapper::getDeviceName( device );
             continue;
         }
         if ( vr::TrackedControllerRole_LeftHand == ctrlRole )
         {
-            LOG(INFO) << "Controller (L) is: " << ovr_system_wrapper::getDeviceName(device);
+            qInfo() << "Controller (L) is: "
+                    << ovr_system_wrapper::getDeviceName( device );
             continue;
         }
         if ( vr::TrackedControllerRole_RightHand == ctrlRole )
         {
-            LOG(INFO) << "Controller (R) is: " << ovr_system_wrapper::getDeviceName(device);
+            qInfo() << "Controller (R) is: "
+                    << ovr_system_wrapper::getDeviceName( device );
             continue;
         }
     }
-    LOG(INFO)<< "Initilizaion is complete--------------------------------------------------";
+    qInfo() << "Initilizaion is "
+               "complete--------------------------------------------------";
 }
 
 void OverlayController::OnRenderRequest()
@@ -560,6 +567,8 @@ void OverlayController::SetOverlayFromQRhiTexture( QRhiTexture& tex )
         vrTex.eColorSpace = vr::ColorSpace_Auto;
     }
     break;
+// Direct3D exists only on Windows.
+#ifdef _WIN32
     case QRhi::D3D11:
     {
         vrTex.handle = reinterpret_cast<ID3D11Texture2D *>( tex.nativeTexture().object );
@@ -568,6 +577,7 @@ void OverlayController::SetOverlayFromQRhiTexture( QRhiTexture& tex )
     
     }
     break;
+#endif
 #if QT_CONFIG( vulkan )
     case QRhi::Vulkan:
     {
@@ -1425,7 +1435,7 @@ void OverlayController::RotateUniverseCenter(
         // }
         vr::HmdMatrix34_t curPos;
         auto calState = vr::VRChaperone()->GetCalibrationState();
-        LOG( INFO ) << "Calibration State on Rotate is: " << calState;
+        qInfo() << "Calibration State on Rotate is: " << calState;
         if ( universe == vr::TrackingUniverseStanding )
         {
             vr::VRChaperoneSetup()->GetWorkingStandingZeroPoseToRawTrackingPose(
@@ -1440,7 +1450,8 @@ void OverlayController::RotateUniverseCenter(
         {
             //TODO 8/3/26, will see if this causes issues
             //should exclusively happen with openxr
-            LOG(INFO) << "rotating on undefined tracking universe probably openxr";
+            qInfo()
+                << "rotating on undefined tracking universe probably openxr";
             vr::VRChaperoneSetup()->GetLiveSeatedZeroPoseToRawTrackingPose(&curPos);
         }