The Java rules used toolchains of type
`@bazel_tools//tools/jdk:runtime_toolchain_type` for two different
purposes requiring different exec/target platform constraints, which led
to issues when cross-compiling: The runtime added to the runfiles of an
executable Java target has to have constraints on the target platform,
whereas the runtime used to extract the bootclasspath should not have
constraints on the target platform. As a result:
1. `@local_jdk` did not define any target constraints for its runtime,
which allowed the runtime to provide the bootclasspath required by
Android rules, but could also end up building `java_binary` targets that
wouldn't run on the target (see #18265).
2. Remote JDKs defined a target constraint for the their runtimes, which
prevented them from being added to the runfiles of targets they couldn't
run on, but broke Android compilation due to the failure to resolve a
runtime for bootclasspath extraction (see #17085).

This is resolved by adding a third toolchain type,
`bootstrap_runtime_toolchain_type`, that is only used by the
`bootclasspath` rule (realizes
https://github.com/bazelbuild/bazel/issues/17085#issuecomment-1454306360).
Detailed explanations of the different types and their intended
constraints have been added to `@bazel_tools//tools/jdk:BUILD`.

Addressing the cross-compilation errors then required the following
changes:
1. Direct dependencies on the Java runtime have been removed from rules
that do not need them (e.g. `android_library` and `java_binary` with
`create_executable = False`).
3. Implicit dependencies on the Java runtime through the `bootclasspath`
rule have been replaced with dependencies on the bootstrap runtime.
4. `{local,remote}_java_repository` now use the user-provided exec
constraints of the Java toolchain as the target constraints of the
associated runtime.
5. `@local_jdk` uses the auto-detected host constraints as exec
constraints for the local Java toolchain.

Fixes #17085
Fixes #18265
Fixes bazelbuild/rules_java#64

RELNOTES[INC]: Java runtime toolchains created via
`local_java_repository` from
`@bazel_tools//tools/jdk:local_java_repository.bzl`, which includes
`local_jdk`, now have `target_compatible_with` set to the auto-detected
host constraints. This can result in errors about toolchain resolution
failures for `@bazel_tools//tools/jdk:runtime_toolchain_type`,
especially when cross-compiling. These failures can be fixed in the
following ways (listed in decreasing order of preference):
* Replace `java_binary` targets that aren't meant to be run with `bazel
run` or as tools during the build with `java_single_jar` (available in
`@rules_java//java:java_single_jar.bzl`). Such targets do not require a
Java runtime for the target configuration.
* Set `--java_runtime_version=remotejdk_N` for some Java version `N` to
let Bazel choose and download an appropriate remote JDK for the current
target platform. This setting defaults to `local_jdk`, which means that
Bazel can only use the local JDK, which isn't compatible with any other
platform.
* Manually define and register a `local_java_runtime` with no value set
for `exec_compatible_with` (defaults to `[]`) and select it by setting
`--java_runtime_version` to its `name`. This fully restores the previous
behavior, but can result in incorrect results when cross-compiling (see
#18265).

Closes #18262.

Commit
https://github.com/bazelbuild/bazel/commit/f79ca0275e14d7c8fb478bd910ad7fb127440fd8



PiperOrigin-RevId: 574914446
Change-Id: I6cbfb7ffa2fbfd62e5f6fb49532b36be658dfa40

Co-authored-by: Fabian Meumertzheim <fabian@meumertzhe.im>