sandvault: simplify prefix use for write_exec_script.

Co-authored-by: Branch Vincent <branchevincent@gmail.com>

Author: webcoyote

Formula/s/sandvault.rb

@@ -18,8 +18,7 @@ class Sandvault < Formula
 
   def install
     prefix.install "guest", "sv", "sv-clone"
-    bin.write_exec_script "#{prefix}/sv"
-    bin.write_exec_script "#{prefix}/sv-clone"
+    bin.write_exec_script prefix/"sv", prefix/"sv-clone"
   end
 
   test do