Fix version.sh when calling meson outside the source repository

This happens for the Arch Linux package, for example.

Author: arch1t3cht

tools/version.sh

@@ -42,6 +42,10 @@ osx_bundle_sed_path="${builddir}/osx-bundle.sed"
 last_svn_revision=6962
 last_svn_hash="16cd907fe7482cb54a7374cd28b8501f138116be"
 
+git() {
+  command git -C "$srcdir" "$@"
+}
+
 # Check if the commit exists first, it doesn't exist in shallow clones.
 if [ "$(git cat-file -t $last_svn_hash 2> /dev/null)" = "commit" ]; then
   git_revision=$(expr $last_svn_revision + $(git rev-list --count $last_svn_hash..HEAD))