Variables are not set with the deprecated `variables` attribute

[ekouts]

The variables attribute gives a deprecation warning but doesn't work anymore. The export ... command is not emitted in the script. Could be because of #2649 or #2648 maybe?

It works perfectly fine, when the test sets env_vars.

Test to reproduce:

import reframe as rfm
import reframe.utility.sanity as sn

@rfm.simple_test
class CheckVars(rfm.RunOnlyRegressionTest):
    valid_systems = ['*']
    valid_prog_environs = ['*']
    # env_vars = {'VAR': 'FOO'}
    variables = {'VAR': 'FOO'}
    executable = 'echo'
    executable_opts = ['$VAR']

    @sanity_function
    def check_exit(self):
        return sn.assert_found('FOO', self.stdout)

[vkarak]

It's indeed a bug; we don't treat the case where an aliased variable is set in the class body. It seems that the assignment is not delegated correctly to the target variable.