Stop creating an empty cmark directory on the CI, as it's no longer needed by the Swift build-script

Author: finagolfin

README.md

@@ -240,4 +240,4 @@ Finally, it gets [the 5.10.1 source](https://github.com/apple/swift/releases/tag
 tarballs for seven Swift repos and renames them to `llvm-project/`, `swift/`,
 `swift-syntax`, `swift-experimental-string-processing`, `swift-corelibs-libdispatch`,
 `swift-corelibs-foundation`, and `swift-corelibs-xctest`, as required by the Swift
-`build-script`, and creates an empty directory, `mkdir cmark`.
+`build-script`.

get-packages-and-swift-source.swift

@@ -236,10 +236,6 @@ _ = runCommand("patchelf", with: ["--set-rpath", "$ORIGIN",
           "\(sdkPath.appendingPathComponent("usr/lib/libcurl.so"))",
           "\(sdkPath.appendingPathComponent("usr/lib/libxml2.so"))"])
 
-if !fmd.fileExists(atPath: cwd.appendingPathComponent("cmark")) {
-  try fmd.createDirectory(atPath: cwd.appendingPathComponent("cmark"), withIntermediateDirectories: false)
-}
-
 for repo in swiftRepos {
   print("Checking for \(repo) source")
   if !fmd.fileExists(atPath: cwd.appendingPathComponent(repo)) {