add check for existing symlink

Signed-off-by: Anton Troshin <anton@diagrid.io>

src/installer.ts

@@ -232,18 +232,25 @@ async function cacheWindowsDir(
     };
   });
 
-  // iterate through actual cache directory paths and make links
+  // iterate through actual cache directory paths and make links if necessary
   for (const cachePath of actualCacheDirectoryPaths) {
     if (!fs.existsSync(cachePath.actualPath)) {
       core.info(`Creating directory ${cachePath.actualPath}`);
       fs.mkdirSync(path.dirname(cachePath.actualPath), {recursive: true});
-    }
-
+    } else {
+      core.info(`Directory ${cachePath.actualPath} already exists`);
+      // make sure the link is pointing to the actual cache directory
+      let symlinkTarget = fs.readlinkSync(cachePath.defaultPath);
+      if (symlinkTarget !== "") {
+        core.info(`Found link ${cachePath.defaultPath} => ${symlinkTarget}`);
+      } else {
         fs.symlinkSync(cachePath.actualPath, cachePath.defaultPath, 'junction');
         core.info(
           `Created link ${cachePath.defaultPath} => ${cachePath.actualPath}`
         );
       }
+    }
+  }
 
   // make outer code to continue using toolcache as if it were installed on c:
   // restore toolcache root to default drive c: