Debug with GDB on Windows

[Aleksey Gorelov]

The dub build with --verbose option generates the output
```
Generating using build
Configuring dependent testd1, deps:
Performing "debug" build using 
c:\D\ldc2-1.38.0-windows-x64\bin\ldc2.exe for x86_64.
testd1 ~master: building configuration "application"...
c:\D\ldc2-1.38.0-windows-x64\bin\ldc2.exe -gdwarf -O0 -c 
-ofapplication-debug-windows-x86_64-ldc_v1.38.0-6D670FD1992E8FC1
1A1557D635DBD69E\testd1.obj -d-debug -g -w --oq 
-od=application-debug-windows-x86_64-ldc_v1.38.0-6D670FD1992E8FC11A1557D6
35DBD69E\/obj -d-version=Have_testd1 -IC:\TestD1\src 
C:\TestD1\src\app.d -vcolumns
Linking...
c:\D\ldc2-1.38.0-windows-x64\bin\ldc2.exe 
-ofapplication-debug-windows-x86_64-ldc_v1.38.0-6D670FD1992E8FC11A1557D635DBD69
E\testd1.exe 
application-debug-windows-x86_64-ldc_v1.38.0-6D670FD1992E8FC11A1557D635DBD69E\testd1.obj -g

```

Still unclear what is wrong.