(fix) pass --colors:off to Nim compiler properly (#1164)

src/nimble.nim

@@ -193,6 +193,9 @@ proc buildFromDir(pkgInfo: PackageInfo, paths: HashSet[string],
  if options.verbosity == SilentPriority:
  # Hide Nim warnings
  args.add("--warnings:off")
+ if options.noColor:
+ # Disable coloured output
+ args.add("--colors:off")
 
  let binToBuild =
  # Only build binaries specified by user if any, but only if top-level package,
@@ -225,8 +228,8 @@ proc buildFromDir(pkgInfo: PackageInfo, paths: HashSet[string],
  let input = realDir / src.changeFileExt("nim")
  # `quoteShell` would be more robust than `\"` (and avoid quoting when
  # un-necessary) but would require changing `extractBin`
- let cmd = "$# $# --colors:on --noNimblePath $# $# $#" % [
- pkgInfo.getNimBin(options).quoteShell, pkgInfo.backend, join(args, " "),
+ let cmd = "$# $# --colors:$# --noNimblePath $# $# $#" % [
+ pkgInfo.getNimBin(options).quoteShell, pkgInfo.backend, if options.noColor: "off" else: "on", join(args, " "),
  outputOpt, input.quoteShell]
  try:
  doCmd(cmd)