Bug Fix: Check for /etc/debian_version

Code Changes:

[ ] Have the PR Validation Tests been run? See https://github.com/vegastrike/Vega-Strike-Engine-Source/wiki/Pull-Request-Validation
[ ] This is a documentation change only
[x] Build system change

Issues:

Purpose:

What is this pull request trying to do? Check that /etc/debian_version exists Before relying on it existing.

NOTE: The logic was originally setup for Debian distros; however, when run on a non-Debian distro with the Debian Packaging tools installed this file does not exist and in some cases it can cause a problem.

vegastrike / Vega-Strike-Engine-Source

Bug Fix: Check for /etc/debian_version #806

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