git: fixed setup of global ignore file

setup

@@ -1,12 +1,14 @@
 #!/bin/bash
 
+script_dir="$( dirname "$BASH_SOURCE" )"
+
 git_version="$(python -c "import re; print(re.search('\d+(\.\d+)+', '$(git --version)').group())")"
 echo "git version: $git_version"
 
 git config --global user.name 'Fabian Peter Hammerle'
 git config --global user.email 'fabian.hammerle@gmail.com'
 
-git config --global core.excludesfile "${PWD}/gitignore"
+git config --global core.excludesfile "${script_dir}/gitignore"
 
 if [[ $git_version == 1.9* ]]; then
     git config --global push.default simple