fix racy sbang (#33549)

Spack currently creates a temporary sbang that is moved "atomically" in place,
but this temporary causes races when multiple processes start installing sbang.

Let's just stick to an idempotent approach. Notice that we only re-install sbang
if Spack updates it (since we do file compare), and sbang was only touched
18 times in the past 6 years, whereas we hit the sbang tempfile issue
frequently with parallel install on a fresh spack instance in CI.

Also fixes a bug where permissions weren't updated if config changed but
the latest version of the sbang file was already installed.

0 files changed, 0 insertions, 0 deletions