build: finish cross-platform release tooling

scripts/package_windows.sh

@@ -36,3 +36,18 @@ rm -f "$zip"
 (cd "$ROOT/dist" && sha256sum "$(basename "$zip")" >"$(basename "$zip").sha256")
 ls -la "$REL"
 echo "$zip"
+
+# NSIS installer from the same folder (CST_REQUIRE_NSIS=1: fail without makensis).
+setup="$ROOT/dist/cst-agent-$ver-windows-x86_64-setup.exe"
+if command -v makensis >/dev/null; then
+  rm -f "$setup"
+  makensis -V2 -WX -INPUTCHARSET UTF8 -DVERSION="$ver" -DSRCDIR="$REL" \
+    -DOUTFILE="$setup" "$ROOT/scripts/windows/cst-agent.nsi"
+  (cd "$ROOT/dist" && sha256sum "$(basename "$setup")" >"$(basename "$setup").sha256")
+  echo "$setup"
+elif [[ "${CST_REQUIRE_NSIS:-0}" == 1 ]]; then
+  echo "makensis not found" >&2
+  exit 1
+else
+  echo "makensis not found; skipping the installer" >&2
+fi