Keep symlinks in legal subdirectories in linux/macos packages. Remove root legal files that already exist in legal/java.base

[kirill-shirokov]

Description

Symlinks in OpenJDK legal/ subtree are not respected by gradle build files and were replaced by files themselves, which accounted to around extra 2Mb in unarchived distribution. Also, duplicate legal files exist in the root of the package (LICENSE, ASSEMBLY_EXCEPTION, ADDITIONAL_LICENSE_INFO).

For all Linux and MacOS targets, the Gradle build files were modified to allow keeping symlinks already created by OpenJDK jlink during the build process.

By default, symlinks are dereferenced as they used to be. However, when Gradle is invoked with -Pcorretto.keepSymlinks=true flag, the symlinks are kept as symlinks in the produced *.tar.gz, *.deb, *.rpm, *.pkg distribution files.

Note that due to a bug/misfeature with -h option in GNU tar, I had to use bsdtar for creating archives either with or without symlinks, so the Docker images now require bsdtar to be installed. Its package can be named 'bsdtar' or 'libarchive-tools' in different OS.

Motivation and context

Trying to reduce unpacked bundle size

How has this been tested?

By building the following targets:

• installers:linux:apline:tar:build
• installers:linux:universal:tar:build
• installers:linux:universal:deb:build
• installers:linux:universal:rpm:build
• installers:mac:tar:build
• installers:mac:pkg:build

... and verifying that previously regular licence files are replaced with symlinks as in OpenJDK in the each type of packaging

Platform information

Works on OS: Linux (universal), Alpine Linux, MacOS
Applies to version: 21, 25, tip