Flags are not passed correctly to custom tasks
When passing custom flags to custom tasks, the flags are not quoted correctly. I suppose we need to use `quoteShell()` here as well:
https://github.com/nim-lang/nimble/blob/bdc9678e2211cebf843a6f470397d50077f7705f/src/nimblepkg/nimscriptwrapper.nim#L66