install.sh does not detect Alibaba Linux correctly

Version:

latest script

Environment:

Alibaba Linux

Scenario:

./install.sh

Expected Result:

Install a CentOS 7 package

Actual Result:

el 2 x86_64
Getting information for chef stable  for el...
downloading https://omnitruck.chef.io/stable/chef/metadata?v=&p=el&pv=2&m=x86_64
  to file /tmp/install.sh.27014/metadata.txt
trying wget...
ERROR 404
Omnitruck artifact does not exist for version  on platform el

Either this means:
   - We do not support el
   - We do not have an artifact for

This is often the latter case due to running a prerelease or RC version of Chef
or a gem version which was only pushed to rubygems and not omnitruck.

You may be able to set your knife[:bootstrap_version] to the most recent stable
release of Chef to fix this problem (or the most recent stable major version number).

In order to test the version parameter, adventurous users may take the Metadata URL
below and modify the '&v=<number>' parameter until you successfully get a URL that
does not 404 (e.g. via curl or wget).  You should be able to use '&v=11' or '&v=12'
successfully.

If you cannot fix this problem by setting the bootstrap_version, it probably means
that el is not supported.

Metadata URL: https://omnitruck.chef.io/stable/chef/metadata?v=&p=el&pv=2&m=x86_64
[root@iZrj996x25ht5omuhhzod7Z ~]#

Start by inspecting install.sh's platform and distribution detection, then reproduce the command on Alibaba Linux. Verify that the detected platform maps to the CentOS 7 package and that the resulting installation succeeds; no test file is mentioned in the issue.