It's better to follow symlinks recursively in Linux launch script

[ZHOUYue67]

The Linux launch script (bin/code) of vscode finds VSCODE_PATH by resolving the path of itself:

VSCODE_PATH="$(dirname $(readlink $0))/.."

Some users might want to use symlinks that link to symlink of bin/code, then this script will fail to launch vscode, because it only follows one layer of symlinks. To solve this problem, simply add -f option to readlink to resolve the symlinks recursively:

VSCODE_PATH="$(dirname $(readlink -f $0))/.."

A pull request is on the way.