add -d to usage

build

@@ -1,6 +1,6 @@
 #!/bin/sh
 #
-# Usage: build [-m ARCH] [-c CPU] [-i IMAGE]
+# Usage: build [-m ARCH] [-c CPU] [-i IMAGE] [-d CMD]
 #
 # Type `build -h` for help and see https://github.com/romkatv/zsh-bin
 # for full documentation.
@@ -19,7 +19,7 @@ if [ -n "${ZSH_VERSION:-}" ]; then
 fi
 
 usage="$(cat <<\END
-Usage: build [-m ARCH] [-c CPU] [-i IMAGE]
+Usage: build [-m ARCH] [-c CPU] [-i IMAGE] [-d CMD]
 
 Creates an archive containing statically-linked, hermetic,
 relocatable Zsh 5.8. Installation of Zsh from the archive