Windows Support: Fixup Perl build (#29711)

* Add pl2bat to PATH: Windows on Perl requires the script pl2bat.bat
  and Perl to be available to the installer via the PATH. The build
  and dependent environments of Perl on Windows have the install
  prefix bin added to the PATH.
* symlink with win32file module instead of using Executable to
  call mklink (mklink is a shell function and so is not accessible
  in this manner).

lib/spack/llnl/util/symlink.py

@@ -11,10 +11,11 @@
 
 from llnl.util import lang
 
-from spack.util.executable import Executable
-
 is_windows = _platform == 'win32'
 
+if is_windows:
+    from win32file import CreateHardLink
+
 
 def symlink(real_path, link_path):
     """
@@ -53,16 +54,7 @@ def _win32_junction(path, link):
         path = os.path.join(parent, path)
         path = os.path.abspath(path)
 
-    command = "mklink"
-    default_args = [link, path]
-    if os.path.isdir(path):
-        # try using a junction
-        default_args.insert(0, '/J')
-    else:
-        # try using a hard link
-        default_args.insert(0, '/H')
-
-    Executable(command)(*default_args)
+    CreateHardLink(link, path)
 
 
 @lang.memoized