BuildStream should fail to install on unsupported platforms

Background

Currently BuildStream checks for the presence of bwrap binary on Linux but does no equivalent checks for host dependencies on non-Liunux platforms. This means that it is possible to install BuildStream without any errors only to have it fail moments later.

This is mostly an issue for Mac and Windows but is applicable to other platforms too.

Task description

• setup.py does host dependency checks on non-Linux platforms

Acceptance Criteria

BuildStream fails to install when required host dependencies are not met

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