🧑‍💻 Build examples --output option

[thinkyhead]

Fixes #27386

• Fix: Some versions of cp won't copy more than one source file of the same name to the same destination.
• Suppress warnings (with prepended config options) when not exporting.
• Add --output to both build_example and build_all_examples to redirect export / archive to another location.
• Change build_example flag -n to -f to match build_all_examples.
• Add usage to build_example.
• Expand ~ to $HOME in path arguments