Add script to detect/build Go plugins.

hack/buildExternalGoPlugins.sh

@@ -0,0 +1,40 @@
+#!/usr/bin/env sh
+set -e
+
+# We assume one go file per plugin, and the desired name of the plugin .so
+# matches the basename of said go file.
+# Example: ReplacementTransformer.go -> ReplacementTransformer.so
+#
+# We also assume the script is run from a kustomize plugin directory.
+# Usually one of:
+#   - ${HOME}/.config/kustomize/plugin
+#   - ${kustomize_git_repo}/plugin
+plugins_dir="${PWD}"
+command="${1}"
+
+function buildPlugin {
+  pushd "${1}" >& /dev/null
+  plugin_src="$(find "${1}" -name '*.go'|grep -Ev '.*_test.go'|head -n1)"
+  plugin_bin="$(echo "${plugin_src}"|sed 's/\(.*\).go/\1.so/')"
+  if [ "${command}" = "clean" ]; then
+    echo "Deleting ${plugin_bin}"
+    rm -f "${plugin_bin}"
+    return
+  fi
+  echo "Building ${plugin_bin}"
+  go build -buildmode plugin -o "${plugin_bin}" "${plugin_src}"
+  popd >& /dev/null
+}
+
+for goMod in $(find "${plugins_dir}" -name 'go.mod'); do
+  d=$(dirname "${goMod}")
+  # Skip "builtin" plugins in kustomize repo.
+  if [ ! -z "$(echo "${goMod}" | grep -F "/plugin/builtin/")" ]; then
+    continue
+  fi
+  # Skip plugins with only test Go files.
+  if [ -z "$(find "${d}" -maxdepth 1 -name '*.go' | grep -Ev ".*_test.go")" ]; then
+    continue
+  fi
+  buildPlugin "${d}"
+done