Update README.md and add v8-marking-state.patch to address ARM64 compilation issues

Author: fauzanelka

README.md

@@ -69,7 +69,43 @@ git submodule update --init --recursive
 cd ..
 ```
 
-## Step 3: Build GN (Google's Build System) for Cross-Compilation
+## Step 3: Apply Required Patches
+
+Before building, you need to apply a critical patch to fix compilation issues with the V8 engine on ARM64.
+
+### Apply the V8 Patch
+
+Apply a patch file to fix the marking state issue:
+
+```bash
+# Navigate to the qtwebengine chromium directory
+cd C:\qtwebengine\src\3rdparty\chromium
+
+# Create the patch file
+curl -LO https://raw.githubusercontent.com/fauzanelka/qtwebengine-arm64/refs/heads/main/v8-marking-state.patch
+
+# Apply the patch
+git apply v8-marking-state.patch
+```
+
+### Alternative: Manual File Edit
+
+If the patch command fails, you can manually edit the file:
+
+1. Open `C:\qtwebengine\chromium\v8\src\heap\cppgc\marking-state.h` in a text editor
+2. Find line ~361 that contains:
+   ```cpp
+   return MutatorMarkingState::BasicMarkingState::MarkNoPush(header);
+   ```
+3. Replace it with:
+   ```cpp
+   return BasicMarkingState::MarkNoPush(header);
+   ```
+4. Save the file
+
+> **Important**: This patch fixes a C++ compilation error where the qualified name lookup fails on ARM64 builds. Without this patch, the build will fail with compilation errors.
+
+## Step 4: Build GN (Google's Build System) for Cross-Compilation
 
 GN must be built first as a native x64 binary before cross-compiling QtWebEngine.
 
@@ -90,7 +126,7 @@ cmake --build . --parallel
 
 > **Note**: The GN build often fails on the first attempt due to dependency resolution. Running the build command twice typically resolves this issue.
 
-## Step 4: Cross-Compile QtWebEngine/QtPdf for ARM64
+## Step 5: Cross-Compile QtWebEngine/QtPdf for ARM64
 
 ### Open Cross-Compilation Environment
 
@@ -138,7 +174,7 @@ C:\Qt\6.9.0\msvc2022_arm64\bin\qt-configure-module.bat ..\qtwebengine -- -DQT_HO
 cmake --build . --parallel
 ```
 
-## Step 5: Install QtWebEngine/QtPdf
+## Step 6: Install QtWebEngine/QtPdf
 
 After the build is complete, you need to install the libraries. It's recommended to install to a separate directory to avoid conflicts with your native Qt installation.
 
@@ -191,6 +227,11 @@ Compress-Archive -Path ".\*" -DestinationPath "C:\QtWebEngine-6.9.0-ARM64.zip"
 4. **Git Submodule Issues**
    - Run: `git submodule update --init --recursive --force`
 
+5. **V8 Compilation Errors**
+   - Ensure the V8 patch from Step 3 has been applied correctly
+   - Check that the file `chromium/v8/src/heap/cppgc/marking-state.h` contains the corrected line
+   - If you see errors related to `MutatorMarkingState::BasicMarkingState`, the patch wasn't applied
+
 ### Verification
 
 After a successful build and installation, you should find the ARM64 libraries in:

v8-marking-state.patch

@@ -0,0 +1,13 @@
+diff --git a/chromium/v8/src/heap/cppgc/marking-state.h b/chromium/v8/src/heap/cppgc/marking-state.h
+index d3533274ba7..1f42edd7783 100644
+--- a/chromium/v8/src/heap/cppgc/marking-state.h
++++ b/chromium/v8/src/heap/cppgc/marking-state.h
+@@ -358,7 +358,7 @@ class MutatorMarkingState final : public BasicMarkingState {
+   ~MutatorMarkingState() override = default;
+
+   inline bool MarkNoPush(HeapObjectHeader& header) {
+-    return MutatorMarkingState::BasicMarkingState::MarkNoPush(header);
++    return BasicMarkingState::MarkNoPush(header);
+   }
+
+   inline void ReTraceMarkedWeakContainer(cppgc::Visitor&, HeapObjectHeader&);