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+OpenJDK21 is an open source implementation of version 21 (LTS) of the
+Java Development Kit, Standard Edition. It includes tools for
+developing, testing, and running programs written in Java.
+
+This script builds the package from source using the packages listed
+in the .info file (the source tarball plus a binary of the prevous
+version to bootstrap from), so it is not necessary to have a jdk
+package installed to build this package.  (See BIG FAT NOTE below.)
+
+By default, the source package uses all available cores to build the
+package, but this can be controlled by passing CORES=<x> to the script.
+It is HIGHLY recommended to use all available cores as a single-core
+build can take quite a while, especially on slower machines.
+NOTE: The build normally fails with MAKEFLAGS set, but this script
+tempararily unsets so it can proceed.
+
+The source is also able to use ccache to speed up rebuilds.  To enable
+this, pass USE_CCACHE=yes to the script.  NOTE: Some other SBo scripts
+recommend creating cc/c++/gcc/g++ symlinks to ccache in /usr/local/bin
+to use ccache, but this build fails on that, so make sure they are
+removed before running this script.
+
+To test the build, pass TESTS=yes.  This will unpack the jtreg package
+to run the tests.  You should expect to see somewhere in the area of
+about 2 dozen failures and about 2 dozen errors. The reports will be
+saved in $TMP/jtreg-reports if you want to review them.
+
+After installing this package you will need to logout/login to your
+machine as it will add new files to the /etc/profile.d folder.
+
+NOTE: This needs almost 4 GB of storage to build, so if space on your
+/tmp is limited, you may want to adjust $TMP to another partition.
+
+BIG FAT NOTE: If you have ANY JDK installed (jdk, zulu-openjdk,
+OpenJDK, etc.), you MUST first uninstall it, then logout/login to
+clear the JAVA_HOME folder from your $PATH in order to build this
+package, otherwise the build will fail.