RFR: 8236921: Add build target to produce a JDK image suitable for a Graal/SVM build

[Severin Gehwolf]

Hi,

Currently there is no easy way to produce an OpenJDK build which could
subsequently be used to build Substrate VM (part of Graal CE). Basic
building blocks are there, but no actual JDK image is getting produced
with the static libs along side their dynamic counterparts. This patch
addresses this by adding a new target called 'graal-builder-image'
which produces a jdk image in $IMAGES/graal-builder-jdk. It basically
copies over libs from static-libs folder and the jdk folder to assemble
the desired result.

Bug: https://bugs.openjdk.java.net/browse/JDK-8236921
webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8236921/02/webrev/

I've tested this works for some snapshot of JDK 14 (rev 3009b27660be)
and graal at revision d9fb0b7dc35a9a7eb559a5e468bcc4c99e918449.

Thoughts?

Thanks,
Severin