[Bug] Error: Unsupported OS type: msys when i buid in windows os

### Search before asking

- [X] I had searched in the [issues](https://github.com/apache/incubator-doris/issues?q=is%3Aissue) and found no similar issues.

### Version

org.apache.doris
flink-doris-connector-${flink.minor.version}
1.0.0-SNAPSHOT

### What's Wrong?

i have copy custom_env.sh.tpl to custom_env.sh, when i use " sh build.sh --flink 1.12.0 --scala 2.11" to build the project,i got an error: "Error: Unsupported OS type: msys" my os is windows 10,and i user git bash to execute the command.

### What You Expected?

someone can help me?

### How to Reproduce?

_No response_

### Anything Else?

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start by reading build.sh and the copied custom_env.sh.tpl/custom_env.sh files, then run `sh build.sh --flink 1.12.0 --scala 2.11` in Git Bash on Windows. Trace where the `msys` OS value is rejected and verify that the connector build completes successfully on the reported environment.

Written by the indexing model from the issue text.