Update Unix dependencies installation script

[am11]

• Use version-less llvm toolchain on Debian/Ubuntu (Use current version of clang and llvm in Linux prereqs #74811).
• Allow case insensitive OS name (eng/install-native-dependencies.sh macos # or osx).
• Check if distro is Debian or its derivative (apt is a Debian thing).
• Remove sudo to make it work with root (e.g. in a docker container); non-root will get a (readable) error from the system, when higher privileges are needed.
• Fix shellcheck errors and lower the dependency to Unix/Bourne shell script (we were using mixed syntax, now it is unified).

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Issue Details

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• Use version-less llvm toolchain on Debian/Ubuntu (Use current version of clang and llvm in Linux prereqs #74811).
• Allow case insensitive OS name (eng/install-native-dependencies.sh macos # or osx).
• Check if distro is Debian or its derivative (apt is a Debian thing).
• Remove sudo to make it work with root (e.g. in a docker container); non-root will get a (readable) error from the system, when higher privileges are needed.
• Fix shellcheck errors and lower the dependency to Unix/Bourne shell script (we were using mixed syntax, now it is unified).

Author:	am11
Assignees:	-
Labels:	area-Infrastructure, community-contribution
Milestone:	-

[ViktorHofer]

Thanks a ton 🤘