Make /etc/profile.d/path.sh POSIX sh compatible to avoid breaking login dash

[haithamseelawi-synth]

Description of changes

aws-parallelcluster-shared::setup_envars renders /etc/profile.d/path.sh from profile/path.sh.erb. The template uses bash-only syntax (a PATH_REQUIRED_DIRECTORIES=(...) array and [[ ... ]]).

Scripts in /etc/profile.d are sourced (not executed) by the login shell, so the #!/bin/bash shebang is ignored. On Debian/Ubuntu /etc/profile is processed by dash, which has no arrays, so any sh -l login aborts with:

/etc/profile.d/path.sh: 3: Syntax error: "(" unexpected

This breaks tooling that relies on a working login sh on cluster nodes (e.g. remote dev-container / IDE setup steps that read the remote env via sh -lc). Interactive users in bash/zsh don't notice it.

This rewrites the template in portable POSIX sh (a plain for loop + case), preserving the existing behavior: append each required directory to PATH only if not already present, in the same order.

Tests

• sh -n / dash -n on the rendered file: exits 0 (previously exit 2).
• Sourced under dash and bash: PATH gets the required directories, and is idempotent when a directory is already present.
• Added an InSpec regression assertion (sh -n /etc/profile.d/path.sh exits 0) to setup_envars_spec.rb; existing assertions unchanged.

References

• N/A

Checklist

• Pointing to the right branch (develop).
• Behavior-preserving change with an added regression test.
• Commit message describes what and why.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.