Fix Java runtime toolchain resolution in cross-compilation scenarios

.bazelrc

@@ -14,6 +14,9 @@ build:remote_shared --tool_java_runtime_version=rbe_jdk
 build:remote_shared --noexperimental_check_desugar_deps
 
 # Configuration to build and test Bazel on RBE on Ubuntu 18.04 with Java 11
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove this toolchain when .bazelversion is 7.0.0rc2 or later.
+build:ubuntu2004_java11 --extra_toolchains=//:bazel_rbe_java_toolchain_definition
 build:ubuntu2004_java11 --extra_toolchains=@rbe_ubuntu2004_java11//java:all
 build:ubuntu2004_java11 --crosstool_top=@rbe_ubuntu2004_java11//cc:toolchain
 build:ubuntu2004_java11 --extra_toolchains=@rbe_ubuntu2004_java11//config:cc-toolchain
@@ -34,6 +37,9 @@ build:windows --extra_toolchains=@bazel_tools//tools/python:autodetecting_toolch
 
 build:windows_arm64 --platforms=//:windows_arm64
 build:windows_arm64 --extra_toolchains=@local_config_cc//:cc-toolchain-arm64_windows
+# When cross-compiling, the local Java runtime, which is used by default, will not be compatible
+# with the target.
+build:windows_arm64 --java_runtime_version=remotejdk_11
 
 # Enable Bzlmod
 common:bzlmod --enable_bzlmod

BUILD

@@ -2,6 +2,7 @@
 
 load("@bazel_skylib//rules:write_file.bzl", "write_file")
 load("@rules_license//rules:license.bzl", "license")
+load("@rules_java//toolchains:default_java_toolchain.bzl", "default_java_toolchain")
 load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 load("@rules_python//python:defs.bzl", "py_binary")
 load("//src/tools/bzlmod:utils.bzl", "get_canonical_repo_name")
@@ -293,3 +294,19 @@ REMOTE_PLATFORMS = ("rbe_ubuntu2004_java11",)
     )
     for platform_name in REMOTE_PLATFORMS
 ]
+
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove these two targets when .bazelversion is 7.0.0rc2 or later.
+default_java_toolchain(
+    name = "bazel_java_toolchain",
+    bootclasspath = ["@rules_java//toolchains:platformclasspath"],
+    source_version = "11",
+    tags = ["manual"],
+    target_version = "11",
+)
+
+default_java_toolchain(
+    name = "bazel_rbe_java_toolchain",
+    source_version = "11",
+    target_version = "11",
+)

MODULE.bazel

@@ -24,7 +24,7 @@ bazel_dep(name = "zstd-jni", version = "1.5.2-3.bcr.1")
 bazel_dep(name = "blake3", version = "1.3.3.bcr.1")
 bazel_dep(name = "zlib", version = "1.3")
 bazel_dep(name = "rules_cc", version = "0.0.9")
-bazel_dep(name = "rules_java", version = "6.3.1")
+bazel_dep(name = "rules_java", version = "7.0.6")
 bazel_dep(name = "rules_proto", version = "5.3.0-21.7")
 bazel_dep(name = "rules_jvm_external", version = "5.2")
 bazel_dep(name = "rules_python", version = "0.24.0")
@@ -231,10 +231,10 @@ use_repo(
     "remotejdk17_macos_aarch64",
     "remotejdk17_win",
     "remotejdk17_win_arm64",
-    "remotejdk20_linux",
-    "remotejdk20_macos",
-    "remotejdk20_macos_aarch64",
-    "remotejdk20_win",
+    "remotejdk21_linux",
+    "remotejdk21_macos",
+    "remotejdk21_macos_aarch64",
+    "remotejdk21_win",
 )
 
 # =========================================
@@ -309,6 +309,10 @@ register_toolchains("@local_config_winsdk//:all")
 
 register_toolchains("//src/main/res:empty_rc_toolchain")
 
+# Workaround for https://github.com/bazelbuild/bazel/issues/19837.
+# TODO(bazel-team): Remove when .bazelversion is 7.0.0rc2 or later.
+register_toolchains("//:bazel_java_toolchain_definition")
+
 # =========================================
 # Android tools dependencies
 # =========================================