building arm64 wheels with cibuildwheel (uses intel runner)

Temporary fix until https://github.com/github/roadmap/issues/528 is merged

ci-scripts/macos/libpng-patch.sh

@@ -0,0 +1,29 @@
+# Solves issue #1346
+# Deprecate patch when Github Actions provides Apple Silicon runners.
+# WARNING: Only run this in a CI runner
+
+# Issue: klayout depends on libpng, which is loaded by homebrew.
+# But M1 wheels are cross-compiled in an intel host, so by default
+# libpng.dylib has an x86 architecture. This prevents linking the library
+# in the tl library.
+
+# Patch solution: manually download libpng arm64 pre-built library from homebrew
+
+# Reading
+# https://stackoverflow.com/questions/55110564/how-can-i-install-a-homebrew-bottle-designed-for-a-different-previous-version
+# https://github.com/Homebrew/homebrew-core/blob/6abea16e917b12d6af4912736f66eb8d42bf089b/Formula/libpng.rb
+
+export HOMEBREW_NO_INSTALL_CLEANUP=1
+export HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=1
+
+# Check if we're about to build an arm64 wheel. WARNING universal wheels not supported
+if [ "$_PYTHON_HOST_PLATFORM" == "macosx-11.0-arm64" ]
+then
+    # Exit early if done
+    test -f /tmp/libpng-apple-silicon-installed && exit 0
+    curl -L -H "Authorization: Bearer QQ==" -o /tmp/libpng-1.6.39.arm64_big_sur.bottle.1.tar.gz https://ghcr.io/v2/homebrew/core/libpng/blobs/sha256:cf59cedc91afc6f2f3377567ba82b99b97744c60925a5d1df6ecf923fdb2f234
+    brew reinstall -f /tmp/libpng-1.6.39.arm64_big_sur.bottle.1.tar.gz || exit 1
+    touch /tmp/libpng-apple-silicon-installed
+elif [ -f "/tmp/libpng-apple-silicon-installed" ]; then
+    brew reinstall -f libpng && rm -f /tmp/libpng-apple-silicon-installed
+fi