Config option to disable setting S_ISGID bit when creating installation directory (#14479)

* Add config option to disable setting S_ISGID bit when creating installation directory. 

Co-authored-by: Ivan Razumov <ivan.razumov@cern.ch>

etc/spack/defaults/config.yaml

@@ -157,3 +157,7 @@ config:
   # Has no effect on macOS. DO NOT MIX these within the same install tree.
   # See the Spack documentation for details.
   shared_linking: 'rpath'
+
+  # Set to 'false' to allow installation on filesystems that doesn't allow setgid bit
+  # manipulation by unprivileged user (e.g. AFS)
+  config:allow_sgid: true

lib/spack/spack/package_prefs.py

@@ -204,7 +204,7 @@ def get_package_dir_permissions(spec):
     attribute sticky for the directory. Package-specific settings take
     precedent over settings for ``all``"""
     perms = get_package_permissions(spec)
-    if perms & stat.S_IRWXG:
+    if perms & stat.S_IRWXG and spack.config.get('config:allow_sgid', True):
         perms |= stat.S_ISGID
     return perms
 

lib/spack/spack/schema/config.py

@@ -73,6 +73,7 @@
                     {'type': 'null'}
                 ],
             },
+            'allow_sgid': {'type': 'boolean'},
         },
     },
 }