Remove existing cached file before overwrite

The permission for the cache file is set to `0500` by default and
when we try to overwrite this file without removing the current file
it failed with following error because the `CopyFileContents` open
the file with `os.O_RDWR` and since the file doesn't have write permission
thus the error.

```
Unable to download oc [open /home/prkumar/.crc/bin/oc/oc: permission denied] Cannot create dst file '/home/prkumar/.crc/bin/oc/oc'
```

Author: praveenkumar

pkg/crc/cache/cache.go

@@ -85,6 +85,9 @@ func (c *Cache) CacheBinary() error {
 
 	for _, extractedFilePath := range extractedFiles {
 		finalBinaryPath := filepath.Join(c.destDir, filepath.Base(extractedFilePath))
+		// If the file exists then remove it (ignore error) first before copy because with `0500` permission
+		// it is not possible to overwrite the file.
+		os.Remove(finalBinaryPath)
 		err = crcos.CopyFileContents(extractedFilePath, finalBinaryPath, 0500)
 		if err != nil {
 			return err