Passing lots of C flas to the D compilers and DUB

[Alain De Vos]

I pass many flags using dub.
Relevant line in my dub.json,
```
"name": "gparted",
	"dflags-ldc": 
["--gcc=cc","--vcolumns","--oq","--dip1000","--dip25","--safe-stack-layout","--boundscheck=on","--D","--g","--w","--de","--d-debug"]
```

Or just direct command,
```
ldc2 --gcc=cc --vcolumns --oq --dip1000 --dip25 
--safe-stack-layout --boundscheck=on --D --g --w --de --d-debug 
`find . -name \*.d -print`
```