Updated everything, got this odd message:

[Andrew Haley]

aph at arm64:/nfs/zebedee/home/graal/graal-core$ mx -v build
/home/aph/hs/build/linux-aarch64-normal-server-release/images/jdk/bin/java -cp /nfs/zebedee/home/graal/graal-core/mxbuild/.jdk9-internal org.graalvm.compiler.hotspot.JVMCIVersionCheck
Could not find any JDK for building projects with compliance 1.8 (version 1.8)
Enter path of JDK:

...baffled.  My JDK_HOME points to the latest JDK 9 build.
What does it want?

Andrew.