Support for OpenBSD/adJ

[vtamara]

Running bin/jt build (improved with https://github.com/oracle/truffleruby/pull/2737) tries to download JDK-11 but it cannot compile it:

$ unset JAVA_HOME; \
  /home/vtamara/comp/truffle/mx/mx \
  -y \
  fetch-jdk \
  --configuration \
  /home/vtamara/comp/truffle/truffleruby/common.json \
  --java-distribution \
  labsjdk-ce-11 \
  --to \
  /home/vtamara/.mx/jdks \
  --alias \
  /home/vtamara/.mx/jdks/labsjdk-ce-11-jvmci-22.3-b04
No such file or directory - /home/vtamara/comp/truffle/mx/mx
FAILED (pid 82558 exit 1): unset JAVA_HOME; \
  /home/vtamara/comp/truffle/mx/mx \
  -y \
  fetch-jdk \
  --configuration \
  /home/vtamara/comp/truffle/truffleruby/common.json \
  --java-distribution \
  labsjdk-ce-11 \
  --to \
  /home/vtamara/.mx/jdks \
  --alias \
  /home/vtamara/.mx/jdks/labsjdk-ce-11-jvmci-22.3-b04

Installing the standard jdk-11 package for OpenBSD and setting JAVA_HOME produces:

% doas pkg_add jdk-11.0.14.9.1p0v0
% export JAVA_HOME=/usr/local/jdk11/
truffleruby jtportable % bin/jt build
Kernel version changed since last build: "" -> "7"
Error during command: build
/home/vtamara/comp/truffle/truffleruby/tool/jt.rb:596:in `find_java_home': $JAVA_HOME does not seem to point to a JVMCI-enabled JDK (`/usr/local/jdk-11/bin/java -version` does not contain 'jvmci') (RuntimeError)
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:607:in `mx'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:877:in `mx'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:2357:in `sforceimports?'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:2430:in `build_graalvm'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:905:in `build'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:3119:in `main'
        from /home/vtamara/comp/truffle/truffleruby/tool/jt.rb:3128:in `<main>'

Running /usr/local/jdk-11/bin/java -version it produces

openjdk version "11.0.14" 2022-01-18
OpenJDK Runtime Environment (build 11.0.14+9-1)
OpenJDK 64-Bit Server VM (build 11.0.14+9-1, mixed mode)