Handle -R in mysql_config output

[citrus-it]

When building on OmniOS, the build panics with:

  --- stderr
  thread 'main' panicked at /data/omnios-build/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mysqlclient-sys-0.4.0/build.rs:80:17:
  Unexpected output from mysql_config: `-L/opt/ooce/mariadb-10.7/lib/amd64 -R/opt/ooce/mariadb-10.7/lib/amd64 -lmariadb -lnsl -lsocket -ldl -lm -lssl -lcrypto -lz`

This is because the output of mysql_config includes a -R link option because the libraries are in a non-standard location. This patch handles converting -R to an appropriate option.

[weiznich]

Thanks 👍