fix(docker): work around ldconfig segfault under QEMU arm64 emulation

ldconfig crashes (exit 139) on GitHub Actions when cross-compiling arm64
images via QEMU user-space emulation. Two fixes:

1. Both Dockerfiles: temporarily replace ldconfig with a no-op before
   apt-get install, then restore it after. This prevents libc-bin's
   post-install script from triggering the crash.

2. runtime/Dockerfile: use ENV LD_LIBRARY_PATH=/usr/lib/swift/linux
   instead of running ldconfig explicitly, avoiding the crash entirely
   for that step.

Revert the qemu-v10.2.1 version pin in docker.yml — the Dockerfile
changes make the QEMU version irrelevant.

Author: KrisSimon

.github/workflows/docker.yml

@@ -42,8 +42,6 @@ jobs:
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
-        with:
-          image: tonistiigi/binfmt:qemu-v10.2.1
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3

docker/buildsystem/Dockerfile

@@ -16,6 +16,16 @@ LABEL org.opencontainers.image.description="Build environment for compiling ARO
 LABEL org.opencontainers.image.source="https://github.com/arolang/aro"
 LABEL org.opencontainers.image.vendor="ARO Language"
 
+# When cross-compiling for arm64 via QEMU on GitHub Actions, ldconfig segfaults
+# under user-space emulation (exit 139). Replace it with a no-op for the duration
+# of apt-get, then restore the real binary afterwards.
+ARG TARGETARCH
+RUN if [ "$TARGETARCH" = "arm64" ]; then \
+      mv /sbin/ldconfig /sbin/ldconfig.real-bak 2>/dev/null || true; \
+      printf '#!/bin/sh\n' > /sbin/ldconfig; \
+      chmod +x /sbin/ldconfig; \
+    fi
+
 # Install build dependencies including LLVM 20
 RUN apt-get update && apt-get install -y --no-install-recommends \
     libcurl4-openssl-dev \
@@ -34,6 +44,11 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && ln -sf /usr/bin/clang-20 /usr/bin/clang \
     && rm -rf /var/lib/apt/lists/*
 
+# Restore the real ldconfig after apt-get (was replaced for QEMU arm64 compatibility)
+RUN if [ -f /sbin/ldconfig.real-bak ]; then \
+      mv /sbin/ldconfig.real-bak /sbin/ldconfig && ldconfig; \
+    fi
+
 # Create pkg-config file for LLVM
 RUN mkdir -p /usr/lib/pkgconfig && \
     printf '%s\n' \

docker/runtime/Dockerfile

@@ -22,6 +22,16 @@ LABEL org.opencontainers.image.description="Minimal runtime environment for ARO
 LABEL org.opencontainers.image.source="https://github.com/arolang/aro"
 LABEL org.opencontainers.image.vendor="ARO Language"
 
+# When cross-compiling for arm64 via QEMU on GitHub Actions, ldconfig segfaults
+# under user-space emulation (exit 139). Replace it with a no-op for the duration
+# of apt-get, then restore the real binary afterwards.
+ARG TARGETARCH
+RUN if [ "$TARGETARCH" = "arm64" ]; then \
+      mv /sbin/ldconfig /sbin/ldconfig.real-bak 2>/dev/null || true; \
+      printf '#!/bin/sh\n' > /sbin/ldconfig; \
+      chmod +x /sbin/ldconfig; \
+    fi
+
 # Install minimal runtime dependencies
 RUN apt-get update && apt-get install -y --no-install-recommends \
     libcurl4 \
@@ -32,12 +42,20 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libxml2 \
     && rm -rf /var/lib/apt/lists/*
 
+# Restore the real ldconfig after apt-get (was replaced for QEMU arm64 compatibility)
+RUN if [ -f /sbin/ldconfig.real-bak ]; then \
+      mv /sbin/ldconfig.real-bak /sbin/ldconfig; \
+    fi
+
 # Copy Swift runtime libraries from the Swift image
 # We use a multi-stage approach to keep the image minimal
 COPY --from=swift:6.2-jammy /usr/lib/swift/linux/*.so /usr/lib/swift/linux/
 
-# Configure the dynamic linker to find Swift libraries
-RUN echo "/usr/lib/swift/linux" > /etc/ld.so.conf.d/swift.conf && ldconfig
+# Configure the dynamic linker to find Swift libraries.
+# Use ENV rather than running ldconfig to avoid QEMU arm64 emulation issues
+# during cross-compilation. LD_LIBRARY_PATH is respected by all Swift binaries.
+RUN echo "/usr/lib/swift/linux" > /etc/ld.so.conf.d/swift.conf
+ENV LD_LIBRARY_PATH=/usr/lib/swift/linux
 
 # Create non-root user for running applications
 RUN useradd -m -s /bin/bash aro