Nimble doesn't work with --gc:arc

[ghost]

Just to store the info:

nimble.nim:416 - need to add nosinks like

proc (file: string) {.nosinks.} =

download.nim:113 - need to do the same

.map(proc(s: string): tuple[ver: Version, tag: string] {.nosinks.} =

and the most important one - Nimble relies on the fact that after catching the exception the variable initialized in the "try" block still contains useful info (for validation), as shown in packageparser.nim, or for shorter example:

type
  PackageInfo* = object
    myPath*: string ## The path of this .nimble file

proc readPackageInfo(): PackageInfo = 
  result = PackageInfo(mypath: "testlol")
  if result.mypath == "testlol":
    raise newException(ValueError, "testlol")
  echo result.mypath

proc getPkgInfoFromFile*(): PackageInfo =
  ## Reads the specified .nimble file and returns its data as a PackageInfo
  ## object. Any validation errors are handled and echoed as warnings.
  try:
    result = readPackageInfo()
  except ValueError:
    echo "error"
  echo "getPkgInfoFromFile:"
  echo result.mypath

proc getPkgInfo*(): PackageInfo = 
  return getPkgInfoFromFile()

proc downloadPkg*() = 
  let pkginfo = getPkgInfo()
  echo pkginfo.mypath

downloadPkg()

I think this can be considered as relying on undefined behaviour, so this probably should be changed (store PackageInfo as the field in ValidationError ?)