add zeromq package (#7)

Static build of libzmq 4.3.5 providing headers and library for
C/C++ projects that link against zmq.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

zeromq/build.sh

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+set -e
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
+cd "$DIR"
+
+VERSION="4.3.5"
+INSTALL_DIR="$DIR/zeromq/install"
+
+# Idempotent: skip if already built
+if [ -f "$INSTALL_DIR/lib/libzmq.a" ]; then
+  echo "zeromq already present, skipping build."
+  exit 0
+fi
+
+NJOBS="$(nproc 2>/dev/null || sysctl -n hw.ncpu 2>/dev/null || echo 2)"
+
+# Clone
+if [ ! -d "libzmq-src" ]; then
+  git clone --depth 1 --branch "v${VERSION}" https://github.com/zeromq/libzmq.git libzmq-src
+fi
+
+# Build
+PREFIX="$DIR/build/prefix"
+mkdir -p "$DIR/build"
+
+cmake -S libzmq-src -B "$DIR/build" \
+  -DCMAKE_BUILD_TYPE=MinSizeRel \
+  -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=ON \
+  -DCMAKE_INSTALL_PREFIX="$PREFIX" \
+  -DCMAKE_INSTALL_LIBDIR=lib \
+  -DCMAKE_POLICY_VERSION_MINIMUM=3.5 \
+  -DWITH_LIBSODIUM=OFF \
+  -DWITH_TLS=OFF \
+  -DWITH_DOCS=OFF \
+  -DBUILD_TESTS=OFF \
+  -DBUILD_SHARED=OFF \
+  -DBUILD_STATIC=ON \
+  -DENABLE_DRAFTS=OFF
+
+cmake --build "$DIR/build" -j"$NJOBS"
+cmake --install "$DIR/build"
+
+# Copy to package install dir
+rm -rf "$INSTALL_DIR"
+mkdir -p "$INSTALL_DIR"/{lib,include}
+
+# Library
+cp "$PREFIX/lib/libzmq.a" "$INSTALL_DIR/lib/"
+
+# Headers
+cp "$PREFIX/include/zmq.h" "$INSTALL_DIR/include/"
+cp "$PREFIX/include/zmq_utils.h" "$INSTALL_DIR/include/"
+
+# Clean up
+rm -rf libzmq-src "$DIR/build"
+
+echo "Installed zeromq to $INSTALL_DIR"
+du -sh "$INSTALL_DIR"