[BUG] the generated gradlew file does not have the correct permission

The gradlew file in the generated project (like in samples/) is wrong.

If you run .gradlew build in samples/client/petstore/java/okhttp-gson you get:

-bash: ./gradlew: Permission denied

Workaround: run chmod +x gradlew before starting gradle.

I think gradlew is a supporting file. We probably need something like this after generation.

private void setExecutable(Path file) throws IOException {
    Set<PosixFilePermission> perms = new HashSet<PosixFilePermission>();
    //add owners permission
    perms.add(PosixFilePermission.OWNER_READ);
    perms.add(PosixFilePermission.OWNER_WRITE);
    perms.add(PosixFilePermission.OWNER_EXECUTE);
    //add group permissions
    perms.add(PosixFilePermission.GROUP_READ);
    //add others permissions
    perms.add(PosixFilePermission.OTHERS_READ);
    Files.setPosixFilePermissions(Paths.get(file).getAbsolutePath()), perms);
}

Start by reproducing the failure with samples/client/petstore/java/okhttp-gson and inspect how the generated gradlew file is created and copied into that project. Confirm the executable permission is preserved or set during generation, then rerun ./gradlew build without the chmod workaround.