Allow sanity checks using dangling symlinks

When doing short term archiving of model output allow sanity checks
for files to support dangling symlinks.

When archiving directories with symlinks (e.g. ADIOS BP files with
symlinks to it) the directories can get archived before the
symlinks. Allow sanity checks to pass even when the script
finds these dangling symlinks.

Author: jayeshkrishna

CIME/case/case_st_archive.py

@@ -644,7 +644,7 @@ def _archive_restarts_date_comp(
                     srcfile = os.path.join(rundir, histfile)
                     destfile = os.path.join(archive_restdir, histfile)
                     expect(
-                        os.path.exists(srcfile),
+                        os.path.exists(srcfile) or os.path.islink(srcfile),
                         "history restart file {} for last date does not exist ".format(
                             srcfile
                         ),
@@ -662,7 +662,7 @@ def _archive_restarts_date_comp(
                     srcfile = os.path.join(rundir, rfile)
                     destfile = os.path.join(archive_restdir, rfile)
                     expect(
-                        os.path.exists(srcfile),
+                        os.path.exists(srcfile) or os.path.islink(srcfile),
                         "restart file {} does not exist ".format(srcfile),
                     )
                     logger.info(
@@ -678,7 +678,7 @@ def _archive_restarts_date_comp(
                         srcfile = os.path.join(rundir, histfile)
                         destfile = os.path.join(archive_restdir, histfile)
                         expect(
-                            os.path.exists(srcfile),
+                            os.path.exists(srcfile) or os.path.islink(srcfile),
                             "hist file {} does not exist ".format(srcfile),
                         )
                         logger.info("copying {} to {}".format(srcfile, destfile))