Updates sqlcipher to release v4.5.7. This version is based on upstream sqlite
version 3.45.3, which is coincidentaly the same as used by this crate at the
time of this commit.
Replace `$_` by `$0` because `$_` doesn't work when using `sh upgrade.sh`.
Replace `bash` by `sh` because we should not depend on bash.
And also remove unused `CUR_DIR` variable.