Improve PyPy ARM64 QEMU stability with modern QEMU 8.x and JIT workarounds

Two critical improvements for PyPy ARM64 wheel builds on QEMU emulation:

1. Install modern QEMU 8.x using tonistiigi/binfmt
   - Added step BEFORE docker/setup-buildx-action
   - QEMU 8.x is much more stable for PyPy JIT
   - Uses 'docker run --rm --privileged tonistiigi/binfmt --install all'

2. PyPy QEMU stability workarounds in both Dockerfiles
   - ENV PYPY_DISABLE_JIT=1      # Disable JIT compiler
   - ENV PYPY_GC_NTHREADS=1      # Single-threaded GC
   - ENV PYPY_FORCE_CPU_COUNT=1  # Force single CPU

Why these changes:
- PyPy's JIT compiler can be unstable under QEMU ARM64 emulation
- Modern QEMU 8.x has much better ARM64 support than older versions
- Single-threaded execution avoids race conditions in QEMU
- Disabling JIT trades performance for stability (acceptable for CI)

Files modified:
- .github/workflows/wheels-arm64.yml: Add QEMU 8.x install step
- docker/Dockerfile.pypy-bookworm-manylinux-arm64: Add PyPy ENV vars
- docker/Dockerfile.pypy-trixie-manylinux-arm64: Add PyPy ENV vars

This should resolve the recurring PyPy ARM64 build failures on GitHub
Actions runners with QEMU emulation.

Author: oberstet

.github/workflows/wheels-arm64.yml

@@ -101,6 +101,13 @@ jobs:
       # QEMU + Docker Buildx Setup
       # ============================================================
 
+      - name: Install modern QEMU (tonistiigi/binfmt)
+        run: |
+          echo "==> Installing modern QEMU 8.x via tonistiigi/binfmt"
+          echo "This provides much better stability for PyPy on ARM64 emulation"
+          docker run --rm --privileged tonistiigi/binfmt --install all
+          echo "✅ Modern QEMU installed"
+
       - name: Set up QEMU for ARM64 emulation
         uses: docker/setup-qemu-action@v3
         with:

docker/Dockerfile.pypy-bookworm-manylinux-arm64

@@ -6,6 +6,12 @@ LABEL maintainer="The Crossbar.io Project <support@crossbario.com>"
 LABEL manylinux.tag="manylinux_2_36_aarch64"
 LABEL glibc.version="2.36"
 
+# PyPy QEMU stability workarounds
+# Disable JIT compiler and force single-threaded execution for stable QEMU emulation
+ENV PYPY_DISABLE_JIT=1
+ENV PYPY_GC_NTHREADS=1
+ENV PYPY_FORCE_CPU_COUNT=1
+
 # Install build essentials for wheel compilation
 RUN apt-get update && apt-get install -y --no-install-recommends \
     build-essential \

docker/Dockerfile.pypy-trixie-manylinux-arm64

@@ -6,6 +6,12 @@ LABEL maintainer="The Crossbar.io Project <support@crossbario.com>"
 LABEL manylinux.tag="manylinux_2_38_aarch64"
 LABEL glibc.version="2.38"
 
+# PyPy QEMU stability workarounds
+# Disable JIT compiler and force single-threaded execution for stable QEMU emulation
+ENV PYPY_DISABLE_JIT=1
+ENV PYPY_GC_NTHREADS=1
+ENV PYPY_FORCE_CPU_COUNT=1
+
 # Install build essentials for wheel compilation
 RUN apt-get update && apt-get install -y --no-install-recommends \
     build-essential \