config: introduce core.site_cache_dir

dvc/config_schema.py

@@ -150,6 +150,7 @@ SCHEMA = {
         Optional("autostage", default=False): Bool,
         Optional("experiments"): Bool,  # obsoleted
         Optional("check_update", default=True): Bool,
+        "site_cache_dir": str,
         "machine": Lower,
     },
     "cache": {

dvc/repo/__init__.py

@@ -565,7 +565,8 @@ class Repo:
 
         from dvc.fs import GitFileSystem
 
-        cache_dir = platformdirs.site_cache_dir("dvc", "iterative", opinion=True)
+        default = platformdirs.site_cache_dir("dvc", "iterative", opinion=True)
+        cache_dir = self.config["core"].get("site_cache_dir") or default
 
         if isinstance(self.fs, GitFileSystem):
             relparts = ()