ci: make vm_start logs readable by all users

This changes permissions for ${BUILD_DIR}/vm_start_.*_log.txt to 644
to make them readable not only by CI user.

Virtual machine boot log files have 0600 permissions by default. This is
a feature of all functions from Python's 'tempfile' module used.

The only way to change permissions is using a particular call of 'chmod'.

Signed-off-by: Uladzimir Bely <ubely@ilbers.de>

testsuite/vm_boot_test/vm_boot_test.py

@@ -46,6 +46,7 @@ class VmBase(Test):
         fd, output_file = tempfile.mkstemp(suffix='_log.txt',
                                            prefix='vm_start_' + distro + '_' +
                                            arch + '_', dir=build_dir, text=True)
+        os.chmod(output_file, 0o644)
 
         cmdline = start_vm.format_qemu_cmdline(arch, build_dir, distro,
                                                output_file, None)