Gitlab CI: Windows Configs (#43967)

Add support for Gitlab CI on Windows

This PR adds the config changes required to configure and execute
Gitlab pipelines running Windows builds on Windows runners using
the existing Gitlab CI infrastructure (and newly added Windows 
infrastructure).

* Adds support for generating child pipelines dispatched to Windows runners
* Refactors the relevant pre-scripts, scripts, and post scripts to be compatible with Windows
* Adds Windows config section describing Windows jobs
* Adds VTK as Windows build stack (to be expanded later)
* Modifies proj to build on Windows
* Refactors Windows rpath symlinking to avoid system libs and externals

---------

Co-authored-by: Ryan Krattiger <ryan.krattiger@kitware.com>
Co-authored-by: Mike VanDenburgh <michael.vandenburgh@kitware.com>
Co-authored-by: Todd Gamblin <tgamblin@llnl.gov>
Co-authored-by: Scott Wittenburg <scott.wittenburg@kitware.com>

lib/spack/llnl/util/filesystem.py

@@ -2531,8 +2531,14 @@ def establish_link(self):
 
         # for each binary install dir in self.pkg (i.e. pkg.prefix.bin, pkg.prefix.lib)
         # install a symlink to each dependent library
-        for library, lib_dir in itertools.product(self.rpaths, self.library_dependents):
-            self._link(library, lib_dir)
+
+        # do not rpath for system libraries included in the dag
+        # we should not be modifying libraries managed by the Windows system
+        # as this will negatively impact linker behavior and can result in permission
+        # errors if those system libs are not modifiable by Spack
+        if "windows-system" not in getattr(self.pkg, "tags", []):
+            for library, lib_dir in itertools.product(self.rpaths, self.library_dependents):
+                self._link(library, lib_dir)
 
 
 @system_path_filter