--- tool/rbinstall.rb.orig	Wed Dec 12 16:31:45 2018
+++ tool/rbinstall.rb	Wed Dec 12 16:31:53 2018
@@ -514,7 +514,10 @@
 
   def install(src, cmd)
     cmd = cmd.sub(/[^\/]*\z/m) {|n| RbConfig.expand(trans[n])}
+    exe_install(src, cmd)
+  end
 
+  def exe_install(src, cmd)
     shebang, body = open(src, "rb") do |f|
       next f.gets, f.read
     end
@@ -781,8 +784,8 @@
       makedirs(bin_dir)
 
       gemspec.executables.map {|exec|
-        $script_installer.install(File.join(srcdir, 'libexec', exec),
-                                  File.join(bin_dir, exec))
+        $script_installer.exe_install(File.join(srcdir, 'libexec', exec),
+                                      File.join(bin_dir, exec))
       }
     end
   end