`--forceConsistentCasingInFilenames` complains when `cwd` has incorrect casing

To reproduce:

```
mkdir CapItalIzation
cd capitalization
echo 'import x from "./b";' > a.ts
echo 'export default 0;' > b.ts
npm install typescript@next
node node_modules/typescript/lib/tsc a.ts b.ts --forceConsistentCasingInFilenames --noEmit
```

The error is:

```
error TS1149: File name 'b.ts' differs from already included file name 'C:/CapItalIzation/b.ts' only in casing
```
