Cannot build Gerrit with JDK9

[davido]

On most recent Bazel master (7574d84) the most recent Gerrit master (b0e82956b1e8b4b04d187c26ec6e055beeaedb82) cannot be built any more (it worked already) with JDK9:

$ java --version
openjdk 9.0.4
OpenJDK Runtime Environment (build 9.0.4+12-suse-4.2-x8664)
OpenJDK 64-Bit Server VM (build 9.0.4+12-suse-4.2-x8664, mixed mode)
$ b9 build --host_java_toolchain=@bazel_tools//tools/jdk:toolchain_java9 --java_toolchain=@bazel_tools//tools/jdk:toolchain_java9 :release
DEBUG: /home/davido/.cache/bazel/_bazel_davido/27a001f4182820ef315d8d2d4f1edafe/external/bazel_skylib/lib/versions.bzl:98:7: 
Current Bazel is not a release version, cannot check for compatibility.
DEBUG: /home/davido/.cache/bazel/_bazel_davido/27a001f4182820ef315d8d2d4f1edafe/external/bazel_skylib/lib/versions.bzl:99:7: Make sure that you are running at least Bazel 0.14.0.
INFO: Analysed target //:release (0 packages loaded).
INFO: Found 1 target...
ERROR: /home/davido/projects/gerrit/java/com/google/gerrit/launcher/BUILD:3:1: Building java/com/google/gerrit/launcher/liblauncher-class.jar (1 source file) failed (Exit 1)
Fatal Error: Unable to find package java.lang in classpath or bootclasspath
Target //:release failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.064s, Critical Path: 0.16s
INFO: 5 processes: 4 remote cache hit, 1 linux-sandbox.
FAILED: Build did NOT complete successfully

[davido]

It worth noting, that upcoming Bazel 0.16.1 release (tested with rc2 from https://releases.bazel.build/0.16.1/rc2/index.html) doesn't seem to be affected: [1]. Only Bazel 0.17.0rc1 and master are affected.

[1] http://paste.openstack.org/show/728089

[cushon]

cc @buchgr

The regression was from updating the embedded JDK to 10 in 4c9149d. The javac we use doesn't support --release when running on JDK 10 yet.

Setting --server_javabase= to JDK 9 works around the problem.

The fix is to update to the JDK 10 javac, but we can't do that until we're ready to drop support for JDK 8 --host_javabases in the default toolchain.