add --debug option to setup.py

[breznak]

Fixes: #1906

[breznak]

@rhyolight ok when 🍏 ?

[rhyolight]

I would make this simpler by updating getCommandLineOption() to handle None. Then you could just make it:

if getCommandLineOption("debug", cmdOptions):
    ...
else if getCommandLineOption("optimizations-native", cmdOptions):
    ...
else if getCommandLineOption("optimizations-lto", cmdOptions):
    ...

[breznak]

nah, you don't want "optimizations-native" and "optimizations-lto" in separate `else if` branches, that's preventing this nicer solution.

[rhyolight]

Whoops, I meant:

if getCommandLineOption("debug", cmdOptions):
    ...
else:
    if getCommandLineOption("optimizations-native", cmdOptions):
        ...
    else if getCommandLineOption("optimizations-lto", cmdOptions):
        ...

This just prevents all the null-checks and makes it easier to read.

[breznak]

Thanks @rhyolight looks better now!