Bazel: Support building with Java 9

Bazel@HEAD supports Java 9.

The current code has one single issue with Java 9 compliance: the usage
of javax.xml.bind.DatatypeConverter class for printHexBinary() method.
This class is not available on Java 9. One alternative is to use guava
library. Something similar was done here: [1]. But unlike the case with
checkstyle library, JGit currently doesn't use guava. Instead, we add
java.xml.bind module with --add-modules compiler option.

To build (or test) with Java 9, build custom bazel version and issue:

  $ bazel --host_javabase=/usr/lib64/jvm/java-9-openjdk build \
    --javacopt='--release 9' \
    --java_toolchain=@bazel_tools//tools/jdk:toolchain_jdk9 :all

The Java 9 support is backwards compatible.

* [1] https://github.com/checkstyle/checkstyle/issues/5027

Change-Id: I2c5203fc4e65885ce7b210f824fda85ba6d6c51d
Signed-off-by: David Ostrovsky <david@ostrovsky.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/BUILD b/BUILD
index be6dd767d5..5fea669f73 100644
--- a/BUILD
+++ b/BUILD
@@ -1,5 +1,12 @@
 package(default_visibility = ["//visibility:public"])
 
+config_setting(
+    name = "jdk9",
+    values = {
+        "java_toolchain": "@bazel_tools//tools/jdk:toolchain_jdk9",
+    },
+)
+
 genrule(
     name = "all",
     testonly = 1,