[feat] Set executable bit in generated job script files

[jgphpc]

Will fix #1679

[pep8speaks]

Hello @jgphpc, Thank you for updating!

Cheers! There are no PEP8 issues in this Pull Request!Do see the ReFrame Coding Style Guide

Comment last updated at 2021-01-28 14:47:15 UTC

[codecov-io]

Codecov Report

Merging #1716 (ea6f541) into master (391ef9e) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1716   +/-   ##
=======================================
  Coverage   87.30%   87.31%           
=======================================
  Files          46       46           
  Lines        7649     7653    +4     
=======================================
+ Hits         6678     6682    +4     
  Misses        971      971           

Impacted Files	Coverage Δ
reframe/core/schedulers/local.py	95.79% <ø> (-0.07%)	⬇️
reframe/core/shell.py	95.45% <100.00%> (+0.45%)	⬆️

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[vkarak]

I think this should be handled by the ShellScriptGenerator in reframe/core/shell.py. Then the callers will set it or not accordingly. Also I don't know if it makes more sense to create them always as executable (without being configurable). I don't see a reason why a job script would harm if it's executable.

[vkarak]

I can fix this PR.

[vkarak]

@jenkins-cscs retry dom