Add cmake directory to llvm source distribution

This directory is required for building LLVM now.

Author: nikic

Diff for: src/bootstrap/dist.rs

@@ -753,6 +753,8 @@ fn copy_src_dirs(
             "llvm-project\\llvm",
             "llvm-project/compiler-rt",
             "llvm-project\\compiler-rt",
+            "llvm-project/cmake",
+            "llvm-project\\cmake",
         ];
         if spath.contains("llvm-project")
             && !spath.ends_with("llvm-project")