Describe the bug
When publishing, alr doesn't ask user for installation of external dependancies.

To Reproduce
my_lib depends on libgnutls which is not installed for some reasons
(well, libgnutls is only needed when executing the main program not for building and I want to publish a library thus I don't strictly need to have it installed, thus I'd like to bypass install as I'm not sudoer).

% alr publish my_lib
...
ⓘ Deploying libgnutls=3.7.10...
The system package 'gnutls' is about to be installed.
This action might require admin privileges and impact your system installation.
Do you want Alire to install this system package?
Using default: Yes
Password:
...

The answer is forced to Yes.

Expected Behavior
I'd expect that alr might ask user for installation like:

ⓘ Deploying libgnutls=3.7.10...
The system package 'gnutls' is about to be installed.
This action might require admin privileges and impact your system installation.
Do you want Alire to install this system package?
[Y] Yes  [N] No  [A] Always  (default is Yes) n
warn: Without this system package the build is likely to fail.
Press Enter to continue or Ctrl-C to abort

alr version
alr 2.0.1