nobug - make breakpad build idempotent
nobug - make breakpad build idempotent

This enhances the breakpad script with some prechecks so that the breakpad make target will successfully run idempotently. Additionally it fixes some shellcheck warnings.

Tayamarn/socorro,AdrianGaudebert/socorro,adngdb/socorro,mozilla/socorro,AdrianGaudebert/socorro,adngdb/socorro,AdrianGaudebert/socorro,m8ttyB/socorro,m8ttyB/socorro,mozilla/socorro,adngdb/socorro,Tayamarn/socorro,lonnen/socorro,Tayamarn/socorro,AdrianGaudebert/socorro,m8ttyB/socorro,mozilla/socorro,lonnen/socorro,Tayamarn/socorro,lonnen/socorro,m8ttyB/socorro,mozilla/socorro,adngdb/socorro,lonnen/socorro,m8ttyB/socorro,AdrianGaudebert/socorro,m8ttyB/socorro,adngdb/socorro,adngdb/socorro,mozilla/socorro,AdrianGaudebert/socorro,Tayamarn/socorro,Tayamarn/socorro,mozilla/socorro