* instead of emitting a breakpoint for a debug safety crash,
zig calls a panic function which prints an error message
and a stack trace and then calls abort.
* on freestanding OS, this panic function has a default
implementation of a simple infinite loop.
* users can override the panic implementation by providing
`pub fn panic(message: []const u8) -> unreachable { }`
* workaround for LLVM segfaulting when you try to use cold
calling convention on ARM.
closes#245
07a71fc322