add a bash script for cygwin that collects all needed dlls to run the demo on Windows

Scripts/developer_scripts/cgal_demo_copy_all_dlls_cygwin.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+
+#use this script from inside the build directory of the Polyhedron demo
+
+declare config="Release"
+
+declare target_directory="CGAL_demo_with_dlls"
+if [[ ! -d "$target_directory" ]]
+then
+  mkdir $target_directory
+fi
+
+copy_dll()
+{
+  local dll_full_path="`cygpath --unix --absolute $1`"
+  echo "copy " $dll_full_path " to " $2
+  cp $dll_full_path $2
+}
+
+
+files=($config/*.exe)
+files+=($config/*.dll)
+files+=(Plugins/*/$config/*.dll)
+
+for file in "${files[@]}"; do
+
+  # copy exe or dll
+  copy_dll $file $target_directory
+
+  # list and copy dependencies
+  cygcheck $file | while read -r dll ; do
+  
+    copy_dll $dll $target_directory
+  
+  done; #check dependencies
+    
+done #loop over directories