Fix illegal reflective access warning on JDK 11 (fixes #12167)

[gnodet]

Summary

• Set org.jline.terminal.exec.redirectPipeCreationMode=native in both mvn and mvn.cmd launcher scripts to prevent JLine's ExecTerminalProvider from using reflection to access ProcessBuilder$RedirectPipeImpl
• This avoids the "WARNING: Illegal reflective access" messages on JDK 9-15 when stdout is redirected (e.g. mvn -v | cat or mvn -v > file.txt)

The property is a JLine 3.x configuration knob (see jline/jline3#951) that switches pipe creation from reflection-based to native (JNI), which is already available since Maven ships jline-terminal-jni and sets -Dlibrary.jline.path.

Fixes #12167

Test plan

• On JDK 11, verify mvn -v | cat no longer prints the "Illegal reflective access" warning
• On JDK 8, verify mvn -v still works (property is harmless — exec provider falls back)
• On JDK 17+, verify no regressions

🤖 Generated with Claude Code

Claude Code on behalf of Guillaume Nodet

[slawekjaranowski]

confirm, my test:

MAVEN_OPTS='-Dorg.jline.terminal.exec.redirectPipeCreationMode=native,reflection' mvn -v | cat -
Apache Maven 3.10.0-SNAPSHOT (c64fbe4aa7e348a30bfecf8c5118d6d399627301)
Maven home: /Users/slawomir.jaranowski/.sdkman/candidates/maven/current
Java version: 11.0.31, vendor: Eclipse Adoptium, runtime: /Users/slawomir.jaranowski/.sdkman/candidates/java/11.0.31-tem
Default locale: en_PL, platform encoding: UTF-8, time zone: Europe/Warsaw
OS name: "mac os x", version: "26.5.1", arch: "aarch64", family: "mac"