add OpenJDK 21

[tofuHero]

Description

add OpenJDK 21

Checklist

• Build rule all-supported completed successfully
• New installation of package completed successfully
• Package upgrade completed successfully (Manually install the package again)
• Package functionality was tested
• Any needed documentation is updated/created

Type of change

• Bug fix
• New Package
• Package update
• Includes small framework changes
• This change requires a documentation update (e.g. Wiki)

[tofuHero]

I tried to execute make all-supported, but it failed with the message make[4]: *** ../../toolchain/syno-qoriq-rust: No such file or directory. Stop. Then I ran the same command in OpenJDK 17, and the error was the same. This seems to be related to the environment.

However, I tried manually compiling other architectures supported by OpenJDK 17, and there were no issues.

[hgy59]

@tofuHero thanks for this PR.
but please create a dedicated branch and do not use the master branch for PRs.

[hgy59]

However, I tried manually compiling other architectures supported by OpenJDK 17, and there were no issues.

There is no need to build packages for all those different archs.
We have the so called generic archs like x64, armv7 and aarch64

aarch64 is for
rtd1296 rtd1619b armada37xx

armv7 is for
alpine alpine4k armada370 armada375 armada38x armadaxp monaco (comcerto2k)
for DSM 7 comcerto2k is not included in armv7 and needs a dedicated build

x64 is for
apollolake avoton braswell broadwell broadwellnk broadwellnkv2 broadwellntbap bromolow cedarview denverton dockerx64 epyc7002 geminilake grantley purley kvmx64 v1000 r1000 x86 x86_64

To install rust for qoriq you can try to navigate to /spksrc/toolchain/syno-qoriq-6.2.4, then call make clean and make to rebuild the toolchain and install our prebuilt rust toolchain for qoriq again.
But we didn't publish OpenJDK 17 for qoriq, we published for DSM 7 only (can't remember why).