COPY cache from pre built image than generating it at build time

[bharathappali]

I would like to recommend a way to chop down build time due to SCC and also ease of maintenance for SCC related issue/updates. As discussed in this PR comments #338 (comment) , It would be better if we generate SCC on a image (Let's say ubuntu as there is lot of support out there) and copy that across other linux distros based on version of JDK respectively.

Current SCC generation:

• Script gets copied on to every image build and then SCC is generated at build time
• 8 releases (java versions) * 2 products (JDK/JRE) * 10 Linux distros * 2 variants (full/slim) = 320 times the SCC is getting generated.

Suggested SCC generation:

• Script gets copied on to only ubuntu image build and then SCC is generated at build time and the other linux distro builds are scheduled after ubuntu and the SCC gets copied based on java version respectively for other distros from the ubuntu image (adoptopenjdk openj9 image) which is already built
• 8 releases (java versions) * 2 products (JDK/JRE) * 1Linux distro(Ubuntu) * 2 variants (full/slim) = 32 times the SCC will get generated.

As SCC is a package of bytecode and AOT code other distros can copy it and it actually works, You can check out this PR discussion #338 (comment)

@karianna @dinogun Can i have your views on it ? Please correct me if I'm wrong or if there are any other challenges which might come up.

thanks in advance

[bharathappali]

@dinogun I'm thinking to drop this enhancement for now and reopen when needed as the SCC process now doesn't involve the run of eclipse IDE and also we may fall victim for problems like #457 . Current implementation is pretty neat (build which creates the cache uses it) and clear with just a tomcat run.