jpackage explicitly sets R/O permission on app launcher executables [1].

This makes it difficult to build tools honoring the R/O permission to clean app image directories.

There is no specific reason for setting an explicit R/O flag only on app launcher executables in an app image. This is merely a legacy jpackage inherited from the JavaFX jpackager [2] and can be safely abandoned.

[1] https://github.com/openjdk/jdk/blob/18dc186a8f4820ed78c21173713dd127ef512e1f/src/jdk.jpackage/windows/classes/jdk/jpackage/internal/ExecutableRebrander.java#L162
[2] https://github.com/openjdk/jfx11u/blob/1bc63c025ce4c7fddba28755e7ddb3c2cb4018ec/modules/jdk.packager/src/main/java/jdk/packager/internal/legacy/builders/windows/WindowsAppImageBuilder.java#L420