Allow nvm-exec to be linked into individual .nvm directories for system-wide installs with a localized Nodes.

Let's say we have nvm installed in a separate mount, /.socket. NVM_DIR is $HOME/.nvm in /etc/profile.d/nvm.sh. With this setup, users can install Node versions to their home directories without each installing nvm.

nvm install --lts

This works fine as does nvm use --lts. When nvm exec is used though, it fails because it looks for nvm-exec in $NVM_DIR. First fix is to look for nvm-exec in $NVM_DIR. If NVM_DIR does not contain nvm-exec, check $BASH_SOURCE[0]. The second fix is to follow nvm-exec if a symbolic link to determine the proper location of nvm's home. Alternatively we could use a second environment variable, NVM_HOME in exec instead of relying on the directory name of nvm-exec.

nvm-exec

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-DIR="$(command cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+DIR="$(dirname $(realpath "${BASH_SOURCE[0]}"))"
 
 # shellcheck disable=SC1090,SC1091
 \. "$DIR/nvm.sh" --no-use