Windows: Symlink support

To provide Windows-compatible functionality, spack code should use
llnl.util.symlink instead of os.symlink. On non-Windows platforms
and on Windows where supported, os.symlink will still be used.

Use junctions when symlinks aren't supported on Windows (#22583)

Support islink for junctions (#24182)

Windows: Update llnl/util/filesystem

* Use '/' as path separator on Windows.
* Recognizing that Windows paths start with '<Letter>:/' instead of '/'

Co-authored-by: lou.lawrence@kitware.com <lou.lawrence@kitware.com>
Co-authored-by: John Parent <john.parent@kitware.com>

lib/spack/external/macholib/util.py

@@ -6,6 +6,8 @@
 
 from macholib import mach_o
 
+from llnl.util.symlink import symlink
+
 MAGIC = [
     struct.pack("!L", getattr(mach_o, "MH_" + _))
     for _ in ["MAGIC", "CIGAM", "MAGIC_64", "CIGAM_64"]
@@ -140,7 +142,7 @@ def mergetree(src, dst, condition=None, copyfn=mergecopy, srcbase=None):
         try:
             if os.path.islink(srcname):
                 realsrc = os.readlink(srcname)
-                os.symlink(realsrc, dstname)
+                symlink(realsrc, dstname)
             elif os.path.isdir(srcname):
                 mergetree(
                     srcname,

lib/spack/external/pytest-fallback/py/_path/local.py

@@ -12,6 +12,8 @@
 
 from os.path import abspath, normpath, isabs, exists, isdir, isfile, islink, dirname
 
+from llnl.util.symlink import symlink
+
 if sys.version_info > (3,0):
     def map_as_list(func, iter):
         return list(map(func, iter))
@@ -79,7 +81,7 @@ def mklinkto(self, oldname):
     def mksymlinkto(self, value, absolute=1):
         """ create a symbolic link with the given value (pointing to another name). """
         if absolute:
-            py.error.checked_call(os.symlink, str(value), self.strpath)
+            py.error.checked_call(symlink, str(value), self.strpath)
         else:
             base = self.common(value)
             # with posix local paths '/' is always a common base
@@ -87,7 +89,7 @@ def mksymlinkto(self, value, absolute=1):
             reldest = self.relto(base)
             n = reldest.count(self.sep)
             target = self.sep.join(('..', )*n + (relsource, ))
-            py.error.checked_call(os.symlink, target, self.strpath)
+            py.error.checked_call(symlink, target, self.strpath)
 
 def getuserid(user):
     import pwd
@@ -892,7 +894,7 @@ def try_remove_lockfile():
         except OSError:
             pass
         try:
-            os.symlink(src, dest)
+            symlink(src, dest)
         except (OSError, AttributeError, NotImplementedError):
             pass