Bazel: Allow to build and run the tests with JDK 15

To avoid JDK specific bugs in future, like Bug: 568950, and given that
upcoming Bazel release 4.0.0 added support to JDK 15 java toolchain,
add definition for remote JDK 15 to WORKSPACE file and add build and
test instructions.

To build and execute the tests with JDK 15 on Linux run:

  $ bazelisk test \
    --java_toolchain=@remote_java_tools_linux//:toolchain_jdk_15 \
    --host_java_toolchain=@remote_java_tools_linux//:toolchain_jdk_15 \
    --javabase=@openjdk15_linux_archive//:runtime \
    --host_javabase=@openjdk15_linux_archive//:runtime \
    //...

To build and execute the tests with JDK 15 on Mac Os X run:

  $ bazelisk test \
    --java_toolchain=@remote_java_tools_darwin//:toolchain_jdk_15 \
    --host_java_toolchain=@remote_java_tools_darwin//:toolchain_jdk_15 \
    --javabase=@openjdk15_darwin_archive//:runtime \
    --host_javabase=@openjdk15_darwin_archive//:runtime \
    //...

To skip the options on the command line, put them in ~/.bazelrc file:

  build --java_toolchain=@remote_java_tools_linux//:toolchain_jdk_15
  build --host_java_toolchain=@remote_java_tools_linux//:toolchain_jdk_15
  build --javabase=@openjdk15_linux_archive//:runtime
  build --host_javabase=@openjdk15_linux_archive//:runtime

Change-Id: I79d5e99f0c731847a82ce7d4c410855434d85f8d
Signed-off-by: David Ostrovsky <david@ostrovsky.org>

.bazelversion

@@ -1 +1 @@
-3.5.0
+4.0.0rc2

WORKSPACE

@@ -27,6 +27,34 @@ load(
     "maven_jar",
 )
 
+http_archive(
+    name = "openjdk15_linux_archive",
+    build_file_content = """
+java_runtime(name = 'runtime', srcs =  glob(['**']), visibility = ['//visibility:public'])
+exports_files(["WORKSPACE"], visibility = ["//visibility:public"])
+""",
+    sha256 = "0a38f1138c15a4f243b75eb82f8ef40855afcc402e3c2a6de97ce8235011b1ad",
+    strip_prefix = "zulu15.27.17-ca-jdk15.0.0-linux_x64",
+    urls = [
+        "https://mirror.bazel.build/cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-linux_x64.tar.gz",
+        "https://cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-linux_x64.tar.gz",
+    ],
+)
+
+http_archive(
+    name = "openjdk15_darwin_archive",
+    build_file_content = """
+java_runtime(name = 'runtime', srcs =  glob(['**']), visibility = ['//visibility:public'])
+exports_files(["WORKSPACE"], visibility = ["//visibility:public"])
+""",
+    sha256 = "f80b2e0512d9d8a92be24497334c974bfecc8c898fc215ce0e76594f00437482",
+    strip_prefix = "zulu15.27.17-ca-jdk15.0.0-macosx_x64",
+    urls = [
+        "https://mirror.bazel.build/cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-macosx_x64.tar.gz",
+        "https://cdn.azul.com/zulu/bin/zulu15.27.17-ca-jdk15.0.0-macosx_x64.tar.gz",
+    ],
+)
+
 JMH_VERS = "1.21"
 
 maven_jar(