Force Linux line endings for mvnw

[albers]

Without this fix, executing mvnw on Windows in a Cygwin environment fails:

$ ./mvnw validate
./mvnw: line 20: $'\r': command not found
./mvnw: line 35: $'\r': command not found
./mvnw: line 56: syntax error near unexpected token `$'in\r''
'/mvnw: line 56: `case "$(uname)" in

Execution is successful if .mvnw has Linux line endings.

[quarkus-bot]

Failing Jobs - Building 00a8c88

Status	Name	Step	Failures	Logs	Raw logs
✔️	JVM Tests - JDK 11
✔️	JVM Tests - JDK 17
⌛	JVM Tests - JDK 17 Windows	Build	⚠️ Check →	Logs	Raw logs
✔️	JVM Tests - JDK 19
✔️	Maven Tests - JDK 11
⌛	Maven Tests - JDK 11 Windows	Build	⚠️ Check →	Logs	Raw logs
⌛	Native Tests - HTTP	Build	⚠️ Check →	Logs	Raw logs