Fix edge case when looking for .asdf-version

cwd can potentially be a symlink, which breaks asdf logic.
The following command will fail to resolve the path correctly:

    env - PWD=/proc/self/cwd PATH=$HOME/.asdf/shims:/bin ruby --version

This first resolves the real path of cwd before continuing to search
for a .tool-versions file

lib/utils.sh

@@ -243,7 +243,7 @@ parse_legacy_version_file() {
 get_preset_version_for() {
   local plugin_name=$1
   local search_path
-  search_path=$(pwd)
+  search_path=$(realpath "$(pwd)")
   local version_and_path
   version_and_path=$(find_version "$plugin_name" "$search_path")
   local version