Improve link script with rollback when using symlink

[fabpot]

Q	A
Feature PR	symfony/symfony#37915
PR author(s)	@noniagriconomie
Merged in	5.2-dev

[ogizanagi]

This one should probably go to 3.4, as symfony/symfony#37952

[noniagriconomie]

@ogizanagi the doc PR is created, should i rebase it also?

[ogizanagi]

@noniagriconomie : Sure, let's go :)