Add aarch64 linux build of openj9+openjdk11

[knn-k]

The aarch64 linux build of openj9+openjdk11 is wanted.
It can be built manually now using a cross-compiling environment by following the build instructions, and runs in the interpreter mode.

[karianna]

If OpenJ9 is supporting this upstream then we're happy to assist in getting this up and running. I've put it in the Backlog as it needs volunteers

[smlambert]

OpenJ9 is supporting this upstream.

FYI @sxa555 - I cc-ed you on a note from @knn-k so you have context.

We have also completed preliminary testing against developer builds.

[sxa]

@knn-k Can it be built natively instead of with a cross compiler? That would make our setup and implementation easier.

[knn-k]

Unfortunately, no. The build configuration for aarch64 in OpenJ9 assumes cross-compilation at this point.
I will take a look if I can change it for building natively.

[sxa]

Changes ibmruntimes/openj9-openjdk-jdk11#149 and eclipse-openj9/openj9#5321 should enable native compilation

[sxa]

Note, the build will run to completion using --with-openssl=system on Ubunt4un 16.04 with the libssl-dev package installed

[sxa]

Almost there - I've temporarily patched the machine to resolve eclipse-openj9/openj9#5451 but once that's in I'll undo that but it's now live on https://ci.adoptopenjdk.net/job/build-scripts/job/jobs/job/jdk11u/job/jdk11u-linux-aarch64-openj9/

[sxa]

Working other than the fact the build currently needs --disable-warnings-as-errors-openj9 as per eclipse-openj9/openj9#4486 - am hoping we can use another option in production.

[sxa]

The "other option" is now submitted under eclipse-openj9/openj9#5508
I have validated that the ar fix works