rustbuild: Make openssl download more reliable.
rustbuild: Make openssl download more reliable.

1. Add -f flag to curl, so when the server returns 403 or 500 it will fail
   immediately.
2. Moved the checksum part into the retry loop, assuming checksum failure
   is due to broken download that can be fixed by downloading again.

GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust