fix handling of quotes in rpath wrapper

[Flamefire]

In some software the compiler must be invoked with an argument containing a literal single quote which requires escaping in the call. E.g.: gcc -DFOO=\'value\'

However the current rpath wrapper would remove those single quotes causing errors during compilation or erronous behavior of the compiled binary.

Fix by replacing the eval of the rpath_args.py output by readarray -t. An array asignment could be used (CMD_ARGS=( $(rpath_args.py ...) )) but that would break up arguments containing spaces. Quotes from the output are kept literally, so quoting to avoid this is not possible. readarray -t works and is widely available.

Also some minor fixes related to quoting in the bash script template.

Note: I used the NULL separator to separate arguments in the output as there is a (very small) chance an argument to the compiler contains newlines.

[boegel]

@Flamefire Failing tests should be looked into, and meanwhile merge conflicts have emerged as well

[Flamefire]

Resolved the merge conflicts. Test failures were mostly due to --trace output of run_shell_cmd.

I also switched the separator to NULL similar to find -print0 to make it (even more) robust

[Flamefire]

Shall we add a special case to tests to detect the GitHub rate limit and skip/succeed them in PRs?