default nimble file generation breaks when used with --styleChecks:error
It turns out that `srcDir` breaks the case sensitivity check from `styleChecks`, and should either be generated as `srcdir`, or the original declaration should be changed to camel case.

Steps to reproduce:
```bash
nimble init mytestproj
cd mytestproj
echo '--styleChecks:error' > config.nims
nimble build
```