Fix githooks/pre-commit mode.

It should be executable.
Refs #8804
refs #8804 fixing compiler warning under unix

appeared after complex conflicts resolution
Merge branch 'feature/8804_ConverToMDHelperV2' of https://github.com/mantidproject/mantid into feature/8804_ConverToMDHelperV2
Merge branch 'feature/8804_ConverToMDHelperV2' into develop