Add utility script for cross-compile workflow

.github/workflows/get-compiler.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+set -eu
+
+case "$1" in
+"pkgs")
+    get_pkgs
+    ;;
+"ccomp")
+    get_compiler
+    ;;
+*)
+    exit 1
+    ;;
+esac
+
+# Given a GOARCH target, return the GCC for that target.
+case "$GOARCH" in
+"amd64")
+    echo "x86_64-pc-linux-gnu-gcc"
+    ;;
+"arm64")
+    echo "aarch64-linux-gnu-gcc"
+    ;;
+"armhf")
+    echo "arm-linux-gnueabihf-gcc"
+    ;;
+*)
+    echo "gcc" # Send us a pull request if RISC-V ever takes off
+    ;;
+esac
+
+# Given a GOARCH target, return a list of Ubuntu packages needed to compile for that target.
+function get_pkgs() {
+    case "$GOARCH" in
+    "arm64")
+        echo "gcc-aarch64-linux-gnu libc6-dev-arm64-cross"
+        ;;
+    "armhf")
+        echo "gcc-arm-linux-gnueabihf libc6-dev-armhf-cross"
+        ;;
+    "amd64" | *)
+        # We (currently) don't need to install more packages on amd64.
+        ;;
+    esac
+}