fix(cli): CLI errors when run as a non-existent user (#21018)

The CDK home directory was being created in the users home directory,
but this causes an error if for some reason the user does not have a
home directory.

This PR adds some fallback logic so that if the users home directory does not exist it will fall back to
creating a tmp directory.

fix #7937


----

### All Submissions:

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### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/main/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk/lib/util/directories.ts

@@ -2,10 +2,26 @@ import * as fs from 'fs';
 import * as os from 'os';
 import * as path from 'path';
 
+/**
+ * Return a location that will be used as the CDK home directory.
+ * Currently the only thing that is placed here is the cache.
+ *
+ * First try to use the users home directory (i.e. /home/someuser/),
+ * but if that directory does not exist for some reason create a tmp directory.
+ *
+ * Typically it wouldn't make sense to create a one time use tmp directory for
+ * the purpose of creating a cache, but since this only applies to users that do
+ * not have a home directory (some CI systems?) this should be fine.
+ */
 export function cdkHomeDir() {
+  const tmpDir = fs.realpathSync(os.tmpdir());
+  let home;
+  try {
+    home = path.join((os.userInfo().homedir ?? os.homedir()).trim(), '.cdk');
+  } catch {}
   return process.env.CDK_HOME
     ? path.resolve(process.env.CDK_HOME)
-    : path.join((os.userInfo().homedir ?? os.homedir()).trim() || '/', '.cdk');
+    : home || fs.mkdtempSync(path.join(tmpDir, '.cdk')).trim();
 }
 
 export function cdkCacheDir() {
@@ -26,4 +42,4 @@ export function rootDir() {
   }
 
   return _rootDir(__dirname);
-}
+}