Fixed build on FreeBSD

On FreeBSD and other systems bash is not always in /bin/bash.

Further add the `-p` flag to the `mkdir` to not fail if the directory
already exists.

Author: raphaelahrens

publish/UnixBuild.sh

@@ -1,11 +1,11 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 cargo build --release -p luals
 
 if [ -d "dist" ]; then
     rm -rf dist
 fi
 
-mkdir bin
+mkdir -p  bin
 
 cp target/release/lua-language-server bin/