CLI equivalent for 'lib-dir' configuration file option

[axricard]

Hello,

I'm trying to cross-compile with ldc for a `x86_64-windows-msvc` 
target. I followed  
https://wiki.dlang.org/Cross-compiling_with_LDC (using prebuilt 
LDC package for C runtime) and it worked just fine. But I'd like 
to get rid of the `ldc2.conf` file and have the whole work being 
done in command line.

The problem is that I can't find a replacement for the 'lib-dir' 
configuration entry in command line interface. Replacing it with 
`-L=-L$LDC_ROOT/lib-win64/ldc2-1.36.0-windows-x64/ 
-L=-L$LDC_ROOT/lib-win64/ldc2-1.36.0-windows-x64/mingw` doesn't 
work :

``` bash
>> ldc2 -mtriple=x86_64-windows -L=-L$LDC_LIB/ 
>> -L=-L$LDC_LIB/mingw foo.d -defaultlib=phobos2-ldc,druntime-ldc
lld-link: error: undefined symbol: __chkstk
>>> referenced by druntime-ldc.lib(dmain2.obj):(_d_run_main)
>>> referenced by druntime-ldc.lib(dmain2.obj):(_d_run_main)
>>> referenced by druntime-ldc.lib(dmain2.obj):(_d_run_main2)
>>> referenced 5 more times
Error: linking with LLD failed
```


it seems that it has to do with this [snippet in 
druntime](https://github.com/ldc-developers/druntime/blob/ldc/src/rt/msvc.d#L76), but I don't understand what changed between configuration file and cli.

Adding '-L=/alternatename:__chkstk=___chkstk_ms' doesn't solve 
the problem.

Do you have any idea of how to make it work without ldc2.conf 
configuration file ?